diff --git a/src/libslic3r/Fill/Fill.cpp b/src/libslic3r/Fill/Fill.cpp
index 6e3886d6dbb..4d8f6a5eda3 100644
--- a/src/libslic3r/Fill/Fill.cpp
+++ b/src/libslic3r/Fill/Fill.cpp
@@ -290,7 +290,8 @@ void split_solid_surface(size_t layer_id, const SurfaceFill &fill, ExPolygons &n
                                                                [](const Line &s) { return s.a == s.b; }),
                                                 polygon_sections[section_idx].end());
             std::sort(polygon_sections[section_idx].begin(), polygon_sections[section_idx].end(),
-                      [](const Line &a, const Line &b) { return a.a.y() < b.b.y(); });
+                      [](const Line &a, const Line &b) { if (a == b) return false; // Ensure irreflexivity
+                                                         return a.a.y() < b.b.y(); });
         }
 
         Polygons reconstructed_area{};
diff --git a/src/libslic3r/PerimeterGenerator.cpp b/src/libslic3r/PerimeterGenerator.cpp
index 50d86a3d068..624a710902b 100644
--- a/src/libslic3r/PerimeterGenerator.cpp
+++ b/src/libslic3r/PerimeterGenerator.cpp
@@ -3179,7 +3179,7 @@ void PerimeterGenerator::process_arachne()
                     // printf("Layer ID %d, Outer index %d, inner index %d, second inner index %d, maximum internal perimeter %d \n",layer_id,outer,first_internal,second_internal, max_internal);
                     if (outer > -1 && first_internal > -1 && second_internal > -1) { // found all three perimeters to re-order? If not the perimeters will be processed outside in.
                         std::vector<PerimeterGeneratorArachneExtrusion> inner_outer_extrusions; // temporary array to hold extrusions for reordering
-                        inner_outer_extrusions.reserve(max_internal - position + 1); // reserve array containing the number of perimeters before a new island. Variables are array indexes hence need to add +1 to convert to position allocations
+                        inner_outer_extrusions.resize(max_internal - position + 1); // reserve array containing the number of perimeters before a new island. Variables are array indexes hence need to add +1 to convert to position allocations
                         // printf("Allocated array size %d, max_internal index %d, start position index %d \n",max_internal-position+1,max_internal,position);
                         
                         for (arr_j = max_internal; arr_j >=position; --arr_j){ // go inside out towards the external perimeter (perimeters in reverse order) and store all internal perimeters until the first one identified with inset index 2
diff --git a/src/libslic3r/PrintObject.cpp b/src/libslic3r/PrintObject.cpp
index 1530fe655c6..01d7e242c97 100644
--- a/src/libslic3r/PrintObject.cpp
+++ b/src/libslic3r/PrintObject.cpp
@@ -2513,7 +2513,10 @@ void PrintObject::bridge_over_infill()
                                                          [](const Line &s) { return s.a == s.b; }),
                                           polygon_sections[i].end());
                 std::sort(polygon_sections[i].begin(), polygon_sections[i].end(),
-                          [](const Line &a, const Line &b) { return a.a.y() < b.b.y(); });
+                          [](const Line &a, const Line &b) {
+                              if (a == b) return false; // Ensure irreflexivity
+                              return a.a.y() < b.b.y();
+                          });
             }
 
             // reconstruct polygon from polygon sections