I've finished the game. I liked the art of the game. I wish it was able to be rendered at a higher resolution. I also really like how the controls are presented as they're needed. Also the icons over those things that kill you is even though it isn't needed a nice touch. What also stood out to me is the main special mechanic. The dice throwing hand. I really liked the animations on that thing but it was a bit too slow a its thing. If you died because of the dice platforms last try and just want to retry it can get annoying waiting for the hand and the dice to get to their position. As at first it wasn't clear that the dice stopped moving after a time I often tried jumping onto the dice while they're moving which is near impossible with the controls as your jump isn't that high. The jump would instantly feel fairer if it was clearer that the dice stop after a time. In the end I've got to say that playing this game was pretty fun but also frustrating.
(Also, is the music supposed to fade out after the first level? I'm on firefox and you've said that there are issues on firefox. As this is the only issue I would really classify as bug that you haven't listed I either think it's a problem with firefox or it's intentionally)
As you're using Godot I can give you a fix for the player playing the "walk"-animation while jumping. If you are using
move_and_slide(velocity, Vector2.UP) # The Vector2.UP is needed for is_on_floor()
You could do something like this within the place where you check if you want to play the walk animation
if is_on_floor(): pass # Play walk animation else: pass # Play jump/fall animation