Potential fix for anvil issues

core/src/main/java/com/boydti/fawe/jnbt/anvil/MCAFile.java

@@ -670,6 +670,7 @@ public class MCAFile {
                     pool.awaitQuiescence(Long.MAX_VALUE, TimeUnit.MILLISECONDS);
                 }
             }
+            chunks.clear();
         }
         IterableThreadLocal.clean(byteStore1);
         IterableThreadLocal.clean(byteStore2);

core/src/main/java/com/boydti/fawe/jnbt/anvil/MCAQueue.java

@@ -70,6 +70,10 @@ public class MCAQueue extends NMSMappedFaweQueue<FaweQueue, FaweChunk, FaweChunk
         this.hasSky = hasSky;
     }
 
+    public boolean hasParent() {
+        return parent != null || parentNMS != null;
+    }
+
     @Override
     public FaweChunk loadChunk(FaweQueue faweQueue, int x, int z, boolean generate) {
         return getFaweChunk(x, z);

core/src/main/java/com/boydti/fawe/jnbt/anvil/MCAQueueMap.java

@@ -193,6 +193,8 @@ public class MCAQueueMap implements IFaweQueueMap {
         lastZ = Integer.MIN_VALUE;
         lastFileX = Integer.MIN_VALUE;
         lastFileZ = Integer.MIN_VALUE;
+        lastChunk = null;
+        lastFile = null;
         if (!mcaFileMap.isEmpty()) {
             Iterator<Map.Entry<Long, MCAFile>> iter = mcaFileMap.entrySet().iterator();
             boolean result;

core/src/main/java/com/sk89q/worldedit/EditSession.java

@@ -1309,7 +1309,7 @@ public class EditSession extends AbstractDelegateExtent implements HasFaweQueue,
             queue.dequeue();
             return;
         }
-        if (Fawe.isMainThread()) {
+        if (Fawe.isMainThread() && (!(queue instanceof MCAQueue) || ((MCAQueue) queue).hasParent())) {
             SetQueue.IMP.flush(queue);
         } else {
             queue.flush();