diff --git a/src/libnest2d/include/libnest2d/selections/firstfit.hpp b/src/libnest2d/include/libnest2d/selections/firstfit.hpp
index 47442850a..bc230690b 100644
--- a/src/libnest2d/include/libnest2d/selections/firstfit.hpp
+++ b/src/libnest2d/include/libnest2d/selections/firstfit.hpp
@@ -119,9 +119,9 @@ public:
                 for(; j < placers.size() && !was_packed && !cancelled(); j++) {
                     result = placers[j].pack(*it, rem(it, store_));
                     score = result.score();
-                    score_all_plates = std::accumulate(placers.begin(), placers.begin() + j, score,
-                        [](double sum, const Placer& elem) { return sum + elem.score(); });
-                    if (this->unfitindicator_) this->unfitindicator_(it->get().name + " bed_id="+std::to_string(j) + ",score=" + std::to_string(score));
+                    score_all_plates = score;
+                    for (int i = 0; i < placers.size(); i++) { score_all_plates += placers[i].score();}
+                    if (this->unfitindicator_) this->unfitindicator_(it->get().name + " bed_id="+std::to_string(j) + ",score=" + std::to_string(score)+", score_all_plates="+std::to_string(score_all_plates));
 
                     if(score >= 0 && score < LARGE_COST_TO_REJECT) {
                         if (bed_id_firstfit == -1) {
diff --git a/src/libslic3r/Arrange.cpp b/src/libslic3r/Arrange.cpp
index b507a8530..3b4b68341 100644
--- a/src/libslic3r/Arrange.cpp
+++ b/src/libslic3r/Arrange.cpp
@@ -633,17 +633,24 @@ protected:
             score += lambda4 * hasRowHeightConflict + lambda4 * hasLidHeightConflict;
         }
         else {
+            int valid_items_cnt = 0;
+            double height_score = 0;
             for (int i = 0; i < m_items.size(); i++) {
                 Item& p = m_items[i];
                 if (!p.is_virt_object) {
+                    valid_items_cnt++;
                     // 高度接近的件尽量摆到一起
-                    score += (1- std::abs(item.height - p.height) / params.printable_height)
+                    height_score += (1- std::abs(item.height - p.height) / params.printable_height)
                         * norm(pl::distance(ibb.center(), p.boundingBox().center()));
                     //score += LARGE_COST_TO_REJECT * (item.bed_temp - p.bed_temp != 0);
-                    if (!Print::is_filaments_compatible({ item.filament_temp_type,p.filament_temp_type }))
+                    if (!Print::is_filaments_compatible({ item.filament_temp_type,p.filament_temp_type })) {
                         score += LARGE_COST_TO_REJECT;
+                        break;
+                    }
                 }
             }
+            if (valid_items_cnt > 0)
+                score += height_score / valid_items_cnt;
         }
 
         std::set<int> extruder_ids;
@@ -664,9 +671,11 @@ protected:
         }
         // for layered printing, we want extruder change as few as possible
         // this has very weak effect, CAN NOT use a large weight
+        int last_extruder_cnt = extruder_ids.size();
         extruder_ids.insert(item.extrude_ids.begin(), item.extrude_ids.end());
+        int new_extruder_cnt= extruder_ids.size();
         if (!params.is_seq_print) {
-            score += 1 * std::max(0, ((int) extruder_ids.size() - 1));
+            score += 1 * (new_extruder_cnt-last_extruder_cnt);
         }
 
         return std::make_tuple(score, fullbb);