Synchronizing on accessing a lock is pointless.

worldedit-core/src/main/java/com/boydti/fawe/beta/implementation/lighting/NMSRelighter.java

@@ -95,7 +95,7 @@ public class NMSRelighter implements Relighter {
     }
 
     @Override
-    public synchronized ReentrantLock getLock() {
+    public ReentrantLock getLock() {
         return lightingLock;
     }
 

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

@@ -1099,7 +1099,7 @@ public class EditSession extends PassthroughExtent implements AutoCloseable {
         try {
             if (relighter != null && !(relighter instanceof NullRelighter)) {
                 // Only relight once!
-                if (!relighter.getLock().tryLock()) {
+                if (Settings.IMP.LIGHTING.DELAY_PACKET_SENDING && !relighter.getLock().tryLock()) {
                     relighter.getLock().lock();
                     relighter.getLock().unlock();
                 } else {
@@ -1109,6 +1109,9 @@ public class EditSession extends PassthroughExtent implements AutoCloseable {
                         relighter.fixSkyLighting();
                         relighter.fixBlockLighting();
                     }
+                    if (Settings.IMP.LIGHTING.DELAY_PACKET_SENDING) {
+                        relighter.getLock().unlock();
+                    }
                 }
             }
         } catch (Throwable e) {