Hello and thank you >\\\<
Mmh probably it's just that the screen delays, 1 time out of 3 it happens to me too, keep smashing UP until the music stops, it should after a while even though you don't hear the punching sound!
But if it persist tell me (I have a backup file after that)
I'm sorry this happened ;__; I'm trying to figure out what causes it but I can't replicate the error yet. I know it's not the ideal solution but if you want to I can send you a save file from after that part, is that ok? (In that case, do you remember which achievements did you have \ how many medals?)