diff --git a/src/libslic3r/PrintConfig.cpp b/src/libslic3r/PrintConfig.cpp
index 50be57e0f8..c4b3c28ad9 100644
--- a/src/libslic3r/PrintConfig.cpp
+++ b/src/libslic3r/PrintConfig.cpp
@@ -9029,11 +9029,8 @@ void DynamicPrintConfig::update_values_to_printer_extruders(DynamicPrintConfig&
                 //variant index
                 variant_index[e_index] = get_index_for_extruder(e_index+1, id_name, extruder_type, nozzle_volume_type, variant_name);
                 if (variant_index[e_index] < 0) {
-                    BOOST_LOG_TRIVIAL(error) << __FUNCTION__ << boost::format(", Line %1%: could not found extruder_type %2%, nozzle_volume_type %3%, extruder_index %4%")
-                        %__LINE__ %s_keys_names_ExtruderType[extruder_type] % s_keys_names_NozzleVolumeType[nozzle_volume_type] % (e_index+1);
-                    assert(false);
-                    //for some updates happens in a invalid state(caused by popup window)
-                    //we need to avoid crash
+                    // Orca: This is expected during transient UI states (e.g. popup windows),
+                    // fall back to 0 silently.
                     variant_index[e_index] = 0;
                 }
             }
diff --git a/src/slic3r/GUI/Plater.cpp b/src/slic3r/GUI/Plater.cpp
index ef46801722..64274adf19 100644
--- a/src/slic3r/GUI/Plater.cpp
+++ b/src/slic3r/GUI/Plater.cpp
@@ -4050,8 +4050,8 @@ void Sidebar::auto_calc_flushing_volumes_internal(const int modify_id, const int
 
     const std::vector<int>& min_flush_volumes = get_min_flush_volumes(full_config, extruder_id);
 
-    ConfigOptionFloat* flush_multi_opt = project_config.option<ConfigOptionFloat>("flush_multiplier");
-    float flush_multiplier = flush_multi_opt ? flush_multi_opt->getFloat() : 1.f;
+    const auto* flush_multi_opt = project_config.option<ConfigOptionFloats>("flush_multiplier");
+    float flush_multiplier = flush_multi_opt ? (float)flush_multi_opt->get_at(extruder_id) : 1.f;
     std::vector<double> matrix = init_matrix;
     int m_max_flush_volume = Slic3r::g_max_flush_volume;
     unsigned int m_number_of_extruders = (int)(sqrt(init_matrix.size()) + 0.001);