Fixes

src/main/java/com/volmit/iris/engine/modifier/IrisPostModifier.java

@@ -480,10 +480,13 @@ public class IrisPostModifier extends EngineAssignedModifier<BlockData> {
 
 
     public void setPostBlock(int x, int y, int z, BlockData d, int currentPostX, int currentPostZ, Hunk<BlockData> currentData) {
+        synchronized (currentData)
+        {
             if (y < currentData.getHeight()) {
                 currentData.set(x & 15, y, z & 15, d);
             }
         }
+    }
 
     public BlockData getPostBlock(int x, int y, int z, int cpx, int cpz, Hunk<BlockData> h) {
         BlockData b = h.getClosest(x & 15, y, z & 15);