diff --git a/src/sat/smt/user_solver.cpp b/src/sat/smt/user_solver.cpp
index 0204573dc..a4273744b 100644
--- a/src/sat/smt/user_solver.cpp
+++ b/src/sat/smt/user_solver.cpp
@@ -39,8 +39,10 @@ namespace user_solver {
         ctx.attach_th_var(n, this, v);
         expr_ref r(m);
         sat::literal_vector explain;
-        if (ctx.is_fixed(n, r, explain))
+        if (ctx.is_fixed(n, r, explain)) {
             m_prop.push_back(prop_info(explain, v, r));
+            DEBUG_CODE(for (auto lit : explain) VERIFY(s().value(lit) == l_true););
+        }
     }
 
     bool solver::propagate_cb(
@@ -90,8 +92,20 @@ namespace user_solver {
         if (!m_fixed_eh)
             return;
         force_push();
+        if (m_fixed.contains(v))
+            return;
+        m_fixed.insert(v);
+        ctx.push(insert_map<uint_set, unsigned>(m_fixed, v));
         m_id2justification.setx(v, sat::literal_vector(num_lits, jlits), sat::literal_vector());
-        m_fixed_eh(m_user_context, this, var2expr(v), value);
+        for (unsigned i = 0; i < num_lits; ++i)
+            if (s().value(m_id2justification[v][i]) == l_false)
+                m_id2justification[v][i].neg();
+        try {
+            m_fixed_eh(m_user_context, this, var2expr(v), value);
+        }
+        catch (...) {
+            throw default_exception("Exception thrown in \"fixed\"-callback");
+        }
     }
 
     bool solver::decide(sat::bool_var& var, lbool& phase) {
@@ -179,9 +193,9 @@ namespace user_solver {
         sat::literal lit = ctx.internalize(prop.m_conseq, false, false);
         if (s().value(lit) != l_true) {
             auto j = mk_justification(m_qhead);
+            persist_clause(lit, j);            
             s().assign(lit, j);
             ++m_stats.m_num_propagations;
-            persist_clause(lit, j);
         }
     }
 
@@ -193,7 +207,7 @@ namespace user_solver {
         if (m_qhead == m_prop.size() && m_replay_qhead == m_clauses_to_replay.size())
             return false;
         force_push();
-
+        
         bool replayed = false;
         if (m_replay_qhead < m_clauses_to_replay.size()) {
             replayed = true;
@@ -235,11 +249,15 @@ namespace user_solver {
             clause.push_back(ctx.literal2expr(~lit));
         for (auto const& [a,b] : prop.m_eqs)
             clause.push_back(m.mk_not(m.mk_eq(a, b)));
+        
         clause.push_back(ctx.literal2expr(lit));
+        if (m.is_false(clause.back()))
+            clause.pop_back();
 
         m_clauses_to_replay.push_back(clause);
         if (m_replay_qhead + 1 < m_clauses_to_replay.size()) 
             std::swap(m_clauses_to_replay[m_replay_qhead], m_clauses_to_replay[m_clauses_to_replay.size()-1]);
+        ctx.push(value_trail<unsigned>(m_replay_qhead));
         ++m_replay_qhead;
     }
 
@@ -260,6 +278,7 @@ namespace user_solver {
         auto const& prop = m_prop[j.m_propagation_index];
         for (unsigned id : prop.m_ids)
             r.append(m_id2justification[id]);
+        DEBUG_CODE(for (auto lit : r) VERIFY(s().value(lit) == l_true););
         for (auto const& p : prop.m_eqs)
             ctx.add_eq_antecedent(probing, expr2enode(p.first), expr2enode(p.second));
     }
diff --git a/src/sat/smt/user_solver.h b/src/sat/smt/user_solver.h
index 373b046b8..4bdfcf064 100644
--- a/src/sat/smt/user_solver.h
+++ b/src/sat/smt/user_solver.h
@@ -79,6 +79,7 @@ namespace user_solver {
         lbool                           m_next_split_phase = l_undef;
         vector<expr_ref_vector> m_clauses_to_replay;
         unsigned                m_replay_qhead = 0;
+        uint_set                m_fixed;
 
         struct justification {
             unsigned m_propagation_index { 0 };