have you considered a second cocker detent or any other that would trap the ball on the other side. sounds like you have a group of paintballs that are really small.best remedy i can think of at the moment, outside of sizing paint before purchase,which isn't always feasible.
just my 2 cents,having 4 variants of the same thing. i haven't encountered it yet,but it'll happen sooner or later, let us (MCB) know your fix. you could also PM agent smith or check his threads and posts. he's likely got a fix for this or has modded at least one zeus in his time,lol.