Minor spoiler in here about when you first get Skystones! But this is a bug thread, so spoilers at own risk anyway I think.
Platform: PS4
Level: 5
Problem: At the start of the second Skystones match with the chefs, nothing in the game was responding, not even going to the Option menu. I could get back to the PS4 screen, so it wasn't a system freeze. After remembering controller weirdness from before, I saw that while my son had dropped out, the player 2 controller was still on. When I tried to use this controller, everything on the match confirmation menu worked. After I started the match, the Player 1 controller worked fine again!
I have noticed other strange things like this, such as the P2 controller working in a Skalatons mini-game, and allowing movement in the hat confirmation screen when getting a new hat. Even if P1 opened the box, whoever moved the controller to Yes and hit X got to wear the hat. Just seems like some sloppy controller crossover coding.
There is a similar bug in the Wii version of Swap Force too (I don't know if other versions also had the same problem). On the title screen, if Player 2 presses the A button to start the game, the game gets mixed up and thinks the Player 2 controller is actually Player 1, and vice versa. So where it would usually assign Player 1 to do something, it's actually Player 2 that has to perform the action, and vice versa. The only way to fix the glitch is to reset the game and have Player 1 press the A button on title screen.