diff --git a/src/libslic3r/Print.hpp b/src/libslic3r/Print.hpp
index 4f9f9ad1e8..a239224262 100644
--- a/src/libslic3r/Print.hpp
+++ b/src/libslic3r/Print.hpp
@@ -150,15 +150,15 @@ public:
     Layer* 			get_layer(int idx) 		 { return m_layers[idx]; }
     // Get a layer exactly at print_z.
     const Layer*	get_layer_at_printz(coordf_t print_z) const {
-    	auto it = Slic3r::lower_bound_by_predicate(m_layers.begin(), m_layers.end(), [print_z](const Layer *layer) { return layer->print_z < print_z; });
+        auto it = Slic3r::lower_bound_by_predicate(m_layers.begin(), m_layers.end(), [print_z](const Layer *layer) { return layer->print_z < print_z; });
 		return (it == m_layers.end() || (*it)->print_z != print_z) ? nullptr : *it;
 	}
     Layer*			get_layer_at_printz(coordf_t print_z) { return const_cast<Layer*>(std::as_const(*this).get_layer_at_printz(print_z)); }
     // Get a layer approximately at print_z.
     const Layer*	get_layer_at_printz(coordf_t print_z, coordf_t epsilon) const {
-        coordf_t limit = print_z + epsilon;
-    	auto it = Slic3r::lower_bound_by_predicate(m_layers.begin(), m_layers.end(), [limit](const Layer *layer) { return layer->print_z < limit; });
-		return (it == m_layers.end() || (*it)->print_z < print_z - epsilon) ? nullptr : *it;
+        coordf_t limit = print_z - epsilon;
+        auto it = Slic3r::lower_bound_by_predicate(m_layers.begin(), m_layers.end(), [limit](const Layer *layer) { return layer->print_z < limit; });
+        return (it == m_layers.end() || (*it)->print_z > print_z + epsilon) ? nullptr : *it;
 	}
     Layer*			get_layer_at_printz(coordf_t print_z, coordf_t epsilon) { return const_cast<Layer*>(std::as_const(*this).get_layer_at_printz(print_z, epsilon)); }
 
diff --git a/src/slic3r/GUI/BackgroundSlicingProcess.cpp b/src/slic3r/GUI/BackgroundSlicingProcess.cpp
index 53c3ec5ea2..27aa6eaa6d 100644
--- a/src/slic3r/GUI/BackgroundSlicingProcess.cpp
+++ b/src/slic3r/GUI/BackgroundSlicingProcess.cpp
@@ -103,30 +103,25 @@ void BackgroundSlicingProcess::process_fff()
 			GUI::RemovableDriveManager::get_instance().update();
 			bool with_check = GUI::RemovableDriveManager::get_instance().is_path_on_removable_drive(export_path);
 			int copy_ret_val = copy_file(m_temp_output_path, export_path, with_check);
-			if (with_check && copy_ret_val == -2)
-			{
-				std::string err_msg = "Copying of the temporary G-code to the output G-code failed. There might be problem with target device, please try exporting again or using different device. The corrupted output G-code is at " + export_path + ".tmp.";
-				throw std::runtime_error(_utf8(L(err_msg)));
-			}
-			else if (with_check && copy_ret_val == -4)
-			{
-				std::string err_msg = "Copying of the temporary G-code has finnished but the original code at "+ m_temp_output_path +" couldn't be opened during copy check. The output G-code is at " + export_path + ".tmp.";
-				throw std::runtime_error(_utf8(L(err_msg)));
-			}
-			else if (with_check && copy_ret_val == -5)
-			{
-				std::string err_msg = "Copying of the temporary G-code has finnished but the exported code couldn't be opened during copy check. The output G-code is at " + export_path + ".tmp.";
-				throw std::runtime_error(_utf8(L(err_msg)));
-			}
-			else if (copy_ret_val == -3)
-			{
-				std::string err_msg = "Renaming of the G-code after copying to the selected destination folder has failed. Current path is " + export_path + ".tmp. Please try exporting again.";
-				throw std::runtime_error(_utf8(L(err_msg)));
-			}
-			else if ( copy_ret_val != 0)
-			{
-	    		throw std::runtime_error(_utf8(L("Copying of the temporary G-code to the output G-code failed. Maybe the SD card is write locked?")));
+			switch (copy_ret_val){
+			case 0: break; // no error
+			case -2: 
+				throw std::runtime_error((boost::format(_utf8(L("Copying of the temporary G-code to the output G-code failed. There might be problem with target device, please try exporting again or using different device. The corrupted output G-code is at %1%.tmp."))) % export_path).str());
+				break;
+			case -3: 
+				throw std::runtime_error((boost::format(_utf8(L("Renaming of the G-code after copying to the selected destination folder has failed. Current path is %1%.tmp. Please try exporting again."))) % export_path).str()); 
+				break;
+			case -4: 
+				throw std::runtime_error((boost::format(_utf8(L("Copying of the temporary G-code has finished but the original code at %1% couldn't be opened during copy check. The output G-code is at %2%.tmp."))) % m_temp_output_path % export_path).str());
+				break;
+			case -5: 
+				throw std::runtime_error((boost::format(_utf8(L("Copying of the temporary G-code has finished but the exported code couldn't be opened during copy check. The output G-code is at %1%.tmp."))) % export_path).str()); 
+				break;
+			default:
+				throw std::runtime_error(_utf8(L("Copying of the temporary G-code to the output G-code failed. Maybe the SD card is write locked?"))); 
+				break;
 			}
+			
 	    	m_print->set_status(95, _utf8(L("Running post-processing scripts")));
 	    	run_post_process_scripts(export_path, m_fff_print->config());
 	    	m_print->set_status(100, (boost::format(_utf8(L("G-code file exported to %1%"))) % export_path).str());
diff --git a/src/slic3r/GUI/GUI_ObjectList.cpp b/src/slic3r/GUI/GUI_ObjectList.cpp
index a5566de299..f5f5548309 100644
--- a/src/slic3r/GUI/GUI_ObjectList.cpp
+++ b/src/slic3r/GUI/GUI_ObjectList.cpp
@@ -77,7 +77,9 @@ static int extruders_count()
 
 static void take_snapshot(const wxString& snapshot_name) 
 {
-    wxGetApp().plater()->take_snapshot(snapshot_name);
+    Plater* plater = wxGetApp().plater();
+    if (plater)
+        plater->take_snapshot(snapshot_name);
 }
 
 ObjectList::ObjectList(wxWindow* parent) :
@@ -3931,7 +3933,9 @@ void ObjectList::OnEditingDone(wxDataViewEvent &event)
 	m_last_selected_column = -1;
 #endif //__WXMSW__
 
-    wxGetApp().plater()->set_current_canvas_as_dirty();
+    Plater* plater = wxGetApp().plater();
+    if (plater)
+        plater->set_current_canvas_as_dirty();
 }
 
 void ObjectList::show_multi_selection_menu()
diff --git a/src/slic3r/GUI/Tab.cpp b/src/slic3r/GUI/Tab.cpp
index e0cfe5be65..541be423d0 100644
--- a/src/slic3r/GUI/Tab.cpp
+++ b/src/slic3r/GUI/Tab.cpp
@@ -2795,7 +2795,7 @@ void Tab::select_preset(std::string preset_name, bool delete_current)
         if (! canceled) {
             // The preset will be switched to a different, compatible preset, or the '-- default --'.
             m_dependent_tabs.emplace_back((printer_technology == ptFFF) ? Preset::Type::TYPE_FILAMENT : Preset::Type::TYPE_SLA_MATERIAL);
-            if (old_preset_dirty)
+            if (old_preset_dirty && ! new_preset_compatible)
                 dependent.discard_current_changes();
         }
     } else if (printer_tab) {