Thanks for your feedback. Yeah unfortunately there is a problem with multiple person at the start sometimes the collision just won't work and you can't get past the first level x). You are one of the rare people to tell me about the end part I don't really understand why it's happening but I inviete you to check out the game after the game jam cause i'll update it to patch fix all the bugs ;)
Viewing post in A spell to live for jam comments
It could be happening because when you place the checkpoint when the moving platform has moved from it's original spot that when you die the platform goes to it's original spot and that the checkpoint isn't on it anymore. You could make it so when you place a checkpoint on the platform that it goes to the original spot of the platform so that doesn't happen.