Chopping in a Cocker is caused by a bolt closing to soon and slicing the ball in half. This will cause paint, she'll, and all kinds of nastiness to be left in the feed neck and up into the hopper. This would most likely be caused by bad settings, a LPR set to low or going bad, or pump arm \ back block not set right.
If the paint is contained in the breach the ball is feeding correctly and breaking somewhere later in the process. Your settings would be correct and you need to look for another reason. Check for clean detents, no sharp protrusions on the face of the bolt or detents. Try a different kind of paint and a different barrel.
This is not definitive, just my experience from owning and working on my Cockers for many years. I have been known to be wrong more than once.