Check for loop only when it is not start edge of thin part

src/libslic3r/SLA/SupportIslands/UniformSupportIsland.cpp

@@ -579,6 +579,7 @@ void create_supports_for_thin_part(
 
         // detect loop on island part
         const Neighbor *twin = VoronoiGraphUtils::get_twin(*curr.neighbor);
+        if (curr.neighbor != part.center.neighbor){ // not first neighbor
             if (auto process_it = std::find_if(process.begin(), process.end(),
                 [twin](const SupportIn &p) { return p.neighbor == twin; });
                 process_it != process.end()) { // self loop detected
@@ -591,6 +592,7 @@ void create_supports_for_thin_part(
                 curr.neighbor = nullptr;
                 continue;
             }
+        }
 
         // next neighbor is short cut to not push back and pop new_starts
         const Neighbor *next_neighbor = nullptr;