I think I've figured out what's causing this - it's actually to do with destroying the bouncy spike badniks with a hyper dash. This seems to set a couple of bytes where Tails' object variables normally reside that cause terrible problems when he's spawned later - which is the moment the drill hits the ground. If you play a Sonic and Tails game, this won't happen because he's already spawned. But yeah, that glitchy mess? That's Tails, that is. The fix I've put into my source seems to be working and should be in the next version.