Welcome to the QuiltingBoard! I'm not sure what you mean by the case sitting high. If the case isn't properly seated the race/hook won't be able to turn freely around it. I see in picture #2 the left thread is not clearing the curved piece to the left of the feed dogs. Assuming the case is properly seated, I would look to see if this piece is bent down a little? Or if there's a burr or something under it catching the thread and not letting it move through as in picture #1. Also check all surfaces of the bobbin case for burrs as well as the inside of the race/hook area. I have a 401 within reach and will check the bobbin area to see if something jumps out at me.