This might be important

src/main/java/com/gmail/nossr50/skills/unarmed/Unarmed.java

@@ -80,6 +80,7 @@ public class Unarmed {
                 nextSlot++;
             }
         } else if (firstEmpty != -1) {
+            drop.remove();
             dropStack.setAmount(dropAmount);
             inventory.setItem(firstEmpty, dropStack);
             return true;