It sounds like robbing to me. Fighting on the ground is a good sign. I have also noticed bees crawling over the side of the hive in small numbers and bees flying around the top and back of the hive looking for ways in.
Put a robber screen on and the fighting will stop. If you are feeding, feed inside the hive from the top.
Thanks. I am not seeing the bees on the sides or flying around the top trying to get in. I have a telescoping outter cover and certainly bees can get in via the top if they want, but few are doing this (certainly no more bees using the top than before the situation started). I have a robbing screen on order and will try that when it comes in if the fighting doesn't stop, but I am curious to see if there is another explanation for what I am seeing rather than robbing.