Fabse

I can confirm that moving the "return" statement one bracket up fixes the issue on a 1.12.2 server.

This is the diff for a CraftBukkit-Server:

--- a/src/main/java/net/minecraft/server/WorldServer.java
+++ b/src/main/java/net/minecraft/server/WorldServer.java
@@ -630,9 +630,10 @@ public class WorldServer extends World implements IAsyncTaskHandler {
                     if (iblockdata.getMaterial() != Material.AIR && iblockdata.getBlock() == block) {
                         iblockdata.getBlock().b((World) this, blockposition, iblockdata, this.random);
                     }
+
+                    return; // Fix MC-120709
                 }
 
-                return;
             }
 
             i = 1;
--