There is a cave in Feldcroft, once inside you are met with 12 blocks that can be interacted with (Accio). If you pull the wrong ones, the blocks reset. You can pull 6 of the 12 but that is it.
While pulling them an small cutscene happened where something moved in the ceiling, but the area was already wide open when I got in and the chest could just be opened immediately.
It just seems like the puzzle doesn't work? It's just north west of the "North Feldcroft" Floo station.