diff --git a/src/libslic3r/GCode.cpp b/src/libslic3r/GCode.cpp
index 13ca4ced67..6e164e20b6 100644
--- a/src/libslic3r/GCode.cpp
+++ b/src/libslic3r/GCode.cpp
@@ -1484,13 +1484,16 @@ void GCode::_do_export(Print& print, GCodeOutputStream &file, ThumbnailsGenerato
             for (auto layer : object->support_layers())
                 zs.push_back(layer->print_z);
         }
-        std::sort(zs.begin(), zs.end());
-        //BBS: merge numerically very close Z values.
-        auto end_it = std::unique(zs.begin(), zs.end());
-        m_layer_count = (unsigned int)(end_it - zs.begin());
-        for (auto it = zs.begin(); it != end_it - 1; it++) {
-            if (abs(*it - *(it + 1)) < EPSILON)
-                m_layer_count--;
+        if (!zs.empty())
+        {
+            std::sort(zs.begin(), zs.end());
+            //BBS: merge numerically very close Z values.
+            auto end_it = std::unique(zs.begin(), zs.end());
+            m_layer_count = (unsigned int)(end_it - zs.begin());
+            for (auto it = zs.begin(); it != end_it - 1; it++) {
+                if (abs(*it - *(it + 1)) < EPSILON)
+                    m_layer_count--;
+            }
         }
     }
     print.throw_if_canceled();
diff --git a/src/slic3r/GUI/Plater.cpp b/src/slic3r/GUI/Plater.cpp
index fcc362dd21..3b39d2ccf3 100644
--- a/src/slic3r/GUI/Plater.cpp
+++ b/src/slic3r/GUI/Plater.cpp
@@ -4716,6 +4716,7 @@ void Plater::priv::export_gcode(fs::path output_path, bool output_path_on_remova
 unsigned int Plater::priv::update_restart_background_process(bool force_update_scene, bool force_update_preview)
 {
     bool switch_print = true;
+
     //BBS: judge whether can switch print or not
     if ((partplate_list.get_plate_count() > 1) && !this->background_process.can_switch_print())
     {
@@ -11199,7 +11200,8 @@ int Plater::select_plate(int plate_index, bool need_slice)
             {
                 if (need_slice) { //from preview's thumbnail
                     if ((invalidated & PrintBase::APPLY_STATUS_INVALIDATED) || (gcode_result->moves.empty())){
-                        //part_plate->update_slice_result_valid_state(false);
+                        if (invalidated & PrintBase::APPLY_STATUS_INVALIDATED)
+                            part_plate->update_slice_result_valid_state(false);
                         p->process_completed_with_error = -1;
                         p->m_slice_all = false;
                         reset_gcode_toolpaths();