The easy way to remove the hull is spray around it with WD-40 or Kroil etc. Get two or tree dimes and stack them up. Insert dimes from muzzle end. Sometimes a wad will work too.
Get a rod or dowel and drive the dimes/wad against the hull.
There is no chance of scoring or scratching the bore this way.
I know this from having to remove separated hulls from a bad batch of Federal hulls.
I have never had a AA separate. All the Federals separated just above the brass - which is where I would expect it to fail if there is a "burr" on the brass that cuts through the plastic. Your failure point is interesting and could have been caused by a defect in the plastic. It is unlikely you will get more failures if that is the case. Let us know if any other hulls fail in the same location on the hull.
I have noticed that with the batches of New Style AA hulls I use - after 4 or 5 loadings (mild loads) I start getting a few that will split length-wise in the center of the case -- so I now discard after 3 or 4 loads
aa has been up front on this issue these are not the old aa's and were not construced to be reloaded but used as a new shell they imply no warrentee for reloading and it is up to you if you choose to do this I am not related to aa but I do reload them 1 time only they are left on the ground after one time
That hull had a crease or wrinkle in it after it was loaded. This results in a weakness of the plastic kind of like if it had been scored all the way around. You need to watch for these when loading, it happens from time to time.
The New AA hulls will sometimes develop a crease or wrinkle just above the top edge of the basewad. It will weaken the hull during subsequent firings. If you see the crease or wrinkle, it's best to toss the hull. There are some adjustments that can be made to eliminate it. Contact your press manufacturer for help getting it set.
I've never seen one separate that way, but I also don't load hulls with certain defects.
I think your one of your crimp stations is putting stress on that area. If you look at your other hull it has a line staring in about the same exact position. Look right in the middle of the S and U and P.