it happens nearly 100% of the time he spawns in. it is a bug and it’s a near certainty GB won’t fix it. I don’t really expect them to ever fix 99% of the remaining bugs in the game. They just don’t care.
As to Smallums–I think the only way for it to work is to slowly take down his health so he goes from a small stage to a big stage to a small stage again like fish slap does.
the annoying thing, at least for me so far, is he has a 90+% spawn rate. Out of 50 or so tries (which includes multiple save/quits to try and get rid of him) he’s been in all but two or three.