Hello redart,
it is not fix-able and it's only a visual bug, shouldn't be banned in the first place imo. Shane didn't wanted it to be banned since he can't fix it (just visual bugged).
I don't recall Shane officially saying Drain Punch couldn't be fixed. Where do you get this information?
He said it on the Unofficial community discord that he can't fix certain things, this most likely include Drain Punch (I can for sure say that it does include Drain Punch). It is a visual bug duo the spaghetti code PRO is build on.