diff --git a/src/math/lp/cross_nested.h b/src/math/lp/cross_nested.h
index c3771f907..d4940ee37 100644
--- a/src/math/lp/cross_nested.h
+++ b/src/math/lp/cross_nested.h
@@ -30,7 +30,7 @@ public:
 
     void run() {
         vector<nex*> front;
-        cross_nested_of_expr_on_front_elem(&m_e, front, true); // true for trivial form - no change
+        explore_of_expr_on_front_elem(&m_e, front, true); // true for trivial form - no change
     }
 
     static nex* pop_back(vector<nex*>& front) {
@@ -52,6 +52,7 @@ public:
     };
 
     static bool extract_common_factor(nex* c, nex& f, const std::unordered_map<lpvar, occ> & occurences) {
+        TRACE("nla_cn", tout << "c=" << *c << "\n";);
         SASSERT(c->is_sum());
         f.type() = expr_type::MUL;
         SASSERT(f.children().empty());
@@ -78,26 +79,36 @@ public:
         f.simplify();
         * c = nex::mul(f, *c);
         TRACE("nla_cn", tout << "common factor=" << f << ", c=" << *c << "\n";);
-        cross_nested_of_expr_on_front_elem(&(c->children()[1]), front, false);
+        explore_of_expr_on_front_elem(&(c->children()[1]), front, false);
         return true;
     }
+
+    static vector<nex> copy_front(const vector<nex*>& front) {
+       vector<nex> v;
+        for (nex* n: front)
+            v.push_back(*n);
+        return v;
+    }
+
+    static void restore_front(const vector<nex> &copy, vector<nex*>& front) {
+        SASSERT(copy.size() == front.size());
+        for (unsigned i = 0; i < front.size(); i++)
+            *(front[i]) = copy[i];
+    }
     
-    void cross_nested_of_expr_on_front_elem_occs(nex* c, vector<nex*>& front, const std::unordered_map<lpvar, occ> & occurences) {
+    void explore_of_expr_on_front_elem_occs(nex* c, vector<nex*>& front, const std::unordered_map<lpvar, occ> & occurences) {
         if (proceed_with_common_factor(c, front, occurences))
             return;
-        TRACE("nla_cn", tout << "save c=" << *c << "front:"; print_vector_of_ptrs(front, tout) << "\n";);           
+        TRACE("nla_cn", tout << "save c=" << *c << "; front:"; print_vector_of_ptrs(front, tout) << "\n";);           
         nex copy_of_c = *c;
-        vector<nex> copy_of_front;
-        for (nex* n: front)
-            copy_of_front.push_back(*n);
+        vector<nex> copy_of_front = copy_front(front);
         for(auto& p : occurences) {
             SASSERT(p.second.m_occs > 1);
             lpvar j = p.first;
-            cross_nested_of_expr_on_sum_and_var(c, j, front);
+            explore_of_expr_on_sum_and_var(c, j, front);
             *c = copy_of_c;
-            TRACE("nla_cn", tout << "restore c=" << *c << ", m_e=" << m_e << "\n";);   
-            for (unsigned i = 0; i < front.size(); i++)
-                *(front[i]) = copy_of_front[i];
+            TRACE("nla_cn", tout << "restore c=" << *c << ", m_e=" << m_e << "\n";);
+            restore_front(copy_of_front, front);
             TRACE("nla_cn", tout << "restore c=" << *c << "\n";);
             TRACE("nla_cn", tout << "m_e=" << m_e << "\n";);   
         }
@@ -113,7 +124,7 @@ public:
         return out;
     }
 
-    void cross_nested_of_expr_on_front_elem(nex* c, vector<nex*>& front, bool trivial_form) {
+    void explore_of_expr_on_front_elem(nex* c, vector<nex*>& front, bool trivial_form) {
         SASSERT(c->is_sum());
         auto occurences = get_mult_occurences(*c);
         TRACE("nla_cn", tout << "m_e=" << m_e << "\nc=" << *c << ", c occurences=";
@@ -134,30 +145,26 @@ public:
                     cross_nested cn(e_s, m_call_on_result);
                     cn.run();
                 }
-                 
             } else {
                 nex* c = pop_back(front);
-                cross_nested_of_expr_on_front_elem(c, front, trivial_form);     
+                explore_of_expr_on_front_elem(c, front, trivial_form);     
             }
         } else {
-            cross_nested_of_expr_on_front_elem_occs(c, front, occurences);
+            explore_of_expr_on_front_elem_occs(c, front, occurences);
         }
     }
     static char ch(unsigned j) {
         return (char)('a'+j);
     }
     // e is the global expression, c is the sub expressiond which is going to changed from sum to the cross nested form
-    void cross_nested_of_expr_on_sum_and_var(nex* c, lpvar j, vector<nex*> front) {
+    void explore_of_expr_on_sum_and_var(nex* c, lpvar j, vector<nex*> front) {
         TRACE("nla_cn", tout << "m_e=" << m_e << "\nc=" << *c << "\nj = " << ch(j) << "\nfront="; print_vector_of_ptrs(front, tout) << "\n";);
-        split_with_var(*c, j, front);
+        if(split_with_var(*c, j, front))
+            return;
         TRACE("nla_cn", tout << "after split c=" << *c << "\nfront="; print_vector_of_ptrs(front, tout) << "\n";);
         SASSERT(front.size());
-        if (can_be_cross_nested_more(*c)) {
-            cross_nested_of_expr_on_front_elem(c, front, false);
-        } else {
-            nex* n = pop_back(front); TRACE("nla_cn", tout << "n=" << *n <<"\n";);
-            cross_nested_of_expr_on_front_elem(n, front, false); // we got a non-trivial_form
-        }
+        nex* n = pop_back(front); TRACE("nla_cn", tout << "n=" << *n <<"\n";);
+        explore_of_expr_on_front_elem(n, front, false); // we got a non-trivial_form
     }
    static void process_var_occurences(lpvar j, std::unordered_map<lpvar, occ>& occurences) {
         auto it = occurences.find(j);
@@ -214,19 +221,23 @@ public:
     static bool can_be_cross_nested_more(const nex& s) {
         auto e = s;
         e.simplify();
-        TRACE("nla_cn_details", tout << "simplified " << e << "\n";);
+        TRACE("nla_cn", tout << "simplified " << e << "\n";);
         switch (e.type()) {
         case expr_type::SCALAR:
             return false;
         case expr_type::SUM: 
-            if ( !get_mult_occurences(e).empty())
+            if ( !get_mult_occurences(e).empty()) {
+                TRACE("nla_cn", tout << "true for " << e << "\n";);
                 return true;
+            }
             // fall through MUL
         case expr_type::MUL:
             {
                 for (const auto & c: e.children()) {
-                    if (can_be_cross_nested_more(c))
+                    if (can_be_cross_nested_more(c)) {
+                        TRACE("nla_cn", tout << "true for " << e << "\n";);
                         return true;
+                    }
                 }
                 return false;
             }
@@ -260,32 +271,55 @@ public:
         }
     }
 
-    static void update_front_with_split_with_non_empty_b(nex& e, lpvar j, vector<nex*> & front, nex& a, nex& b) {
+    // returns true if the recursion is done inside
+    bool update_front_with_split_with_non_empty_b(nex& e, lpvar j, vector<nex*> & front, nex& a, nex& b) {
         nex f;
         bool a_has_f = extract_common_factor(&a, f, get_mult_occurences(a));
         SASSERT(a.is_sum());
         if (a_has_f) {
             TRACE("nla_cn", tout << "a=" << a << ", f=" << f << "\n";);
             a /= f;
-            e = nex::sum(nex::mul(nex::var(j), f, a), b);
-            TRACE("nla_cn", tout << "a = " << a << ", e = " << e << "\n";);
-            auto& jfa = e.children()[0];
-            SASSERT(jfa.size() == 3);
-            front.push_back(&(jfa.children()[2]));
-            front.push_back(&e); // e might have its own cross nested form
+            auto j_f_a = nex::mul(nex::var(j), f, a);
+            j_f_a.simplify();
+            e = nex::sum(j_f_a, b);
+            TRACE("nla_cn", tout << "j_f_a = " << j_f_a << ", e = " << e << "\n";);
+            e.simplify();
+            auto occs = get_mult_occurences(e);
+            
+            if (occs.empty()) {
+                TRACE("nla_cn", tout << "occs are empty\n";);
+                auto& jfa = e.children()[0];
+                front.push_back(jfa.children().end() - 1);
+            } else {
+                TRACE("nla_cn", tout << "recurse\n";);
+                 nex copy_of_e = e;
+                 vector<nex> copy_of_front = copy_front(front);
+                 for(auto& p : occs) {
+                     SASSERT(p.second.m_occs > 1);
+                     auto& jfa = e.children()[0];
+                     front.push_back(jfa.children().end() - 1);
+                     lpvar j = p.first;
+                     explore_of_expr_on_sum_and_var(&e, j, front);
+                     e = copy_of_e;
+                     front.pop_back();
+                     restore_front(copy_of_front, front);
+                 }
+                 return true;
+            }
         } else {
             TRACE("nla_cn_details", tout << "b = " << b << "\n";);
             e = nex::sum(nex::mul(nex::var(j), a), b);
             front.push_back(&(e.children()[0].children()[1]));
-            TRACE("nla_cn_details", tout << "push to front " << e.children()[0].children()[1] << "\n";);
+            TRACE("nla_cn", tout << "push to front " << e.children()[0].children()[1] << "\n";);
         }
         if (b.is_sum()) {
             front.push_back(&(e.children()[1]));
-            TRACE("nla_cn_details", tout << "push to front " << e.children()[1] << "\n";);
+            TRACE("nla_cn", tout << "push to front " << e.children()[1] << "\n";);
         }
+        return false;
     }
     
-    static void update_front_with_split(nex& e, lpvar j, vector<nex*> & front, nex& a, nex& b) {
+   bool update_front_with_split(nex& e, lpvar j, vector<nex*> & front, nex& a, nex& b) {
         if (b.is_undef()) {
             SASSERT(b.children().size() == 0);
             e = nex(expr_type::MUL);        
@@ -295,18 +329,19 @@ public:
                 front.push_back(&e.children().back());
                 TRACE("nla_cn_details", tout << "push to front " << e.children().back() << "\n";);
             }
-        } else {
-            update_front_with_split_with_non_empty_b(e, j, front, a, b);
+            return false;
         }
-
+        return update_front_with_split_with_non_empty_b(e, j, front, a, b);
     }
-    static void split_with_var(nex& e, lpvar j, vector<nex*> & front) {
-        TRACE("nla_cn_details", tout << "e = " << e << ", j = v" << j << "\n";);
+    // it returns true if the recursion is done inside
+    bool split_with_var(nex& e, lpvar j, vector<nex*> & front) {
+        TRACE("nla_cn", tout << "e = " << e << ", j=" << ch(j) << "\n";);
         if (!e.is_sum())
-            return;
+            return false;
         nex a, b;
+        
         pre_split(e, j, a, b);
-        update_front_with_split(e, j, front, a, b);
+        return update_front_with_split(e, j, front, a, b);
     }
     std::set<lpvar> get_vars_of_expr(const nex &e ) const {
         std::set<lpvar> r;
diff --git a/src/math/lp/nla_expr.h b/src/math/lp/nla_expr.h
index 4ad7ba8f8..fa3936d91 100644
--- a/src/math/lp/nla_expr.h
+++ b/src/math/lp/nla_expr.h
@@ -105,7 +105,7 @@ public:
                 for (auto &e : m_children) {
                     n += e;
                 }
-                *this = n;
+                m_children = n.m_children;
             }        
         } else if (is_mul()) {
             bool has_mul = false;
@@ -118,7 +118,7 @@ public:
                 for (auto &e : m_children) {
                     n *= e;
                 }
-                *this = n;
+                m_children = n.m_children;
             }
             TRACE("nla_cn_details", tout << "simplified " << *this << "\n";);
         }
@@ -320,7 +320,6 @@ public:
         for (; i < children().size(); i++, k++) {
             auto & e = children()[i];
             if (!e.is_var()) {
-                SASSERT(e.is_scalar());
                 continue;
             }
             lpvar j = e.var();
diff --git a/src/test/lp/lp.cpp b/src/test/lp/lp.cpp
index a99a851f9..1396a6167 100644
--- a/src/test/lp/lp.cpp
+++ b/src/test/lp/lp.cpp
@@ -78,8 +78,7 @@ void test_cn_on_expr(horner::nex t) {
 void test_cn() {
     typedef horner::nex nex;
     enable_trace("nla_cn");
-    enable_trace("nla_cn_cn");
-    enable_trace("nla_cn_details");
+    //  enable_trace("nla_cn_details");
     nex a = nex::var(0), b = nex::var(1), c = nex::var(2), d = nex::var(3), e = nex::var(4);
     //    test_cn_on_expr(a*b + a*c + b*c);
     //TRACE("nla_cn", tout << "done\n";);