Whenever you put a compass in an item frame, the FPS sharply decreases. As far as I can tell the bug is entirely client side. There seem to be 2 exceptions to this. If you stand still, the texture won't change, so neither will your FPS. It also seems stable if the item frame isn't rendered. So if you want to prevent this, don't look at the item frame. For some reason, this can not be done with clocks. I attached some screenshots to show my FPS when I put a compass in an item frame. The first is the frame without a compass, the second is with a compass, the third is when looking away.
EDIT: Turns out it only happens when using a resource pack. But I still think it's important enough to fix.