Can't move pieces

Well I have experiences with pieces vanishing and not loading in puzzle races, when after the puzzle racer starts the board is empty and I after I use the skip option lichess does not allow me to move the pieces. My problem is slightly different to your but mine is because of slow internet and this happens pretty frequently. Usually it is a 10% chance for this to occur in my case.

I think you might have to delete that study :( and create a new one.