Needle hitting the bobbing case

Question

Hi. I have a Pfaff classic style quilt 2027. I have had it in the shop multiple times but it keeps coming back with the same problem. The needle hits the bobbin case.

It will work for a short time then the upper thread starts to loop on the underside of the fabric. I follow my manuals instructions everytime. I very gently snip the threads top and bottom so I can remove the fabric without pulling then I use tweezers to remove the bits of thread left over and the little brush to get rid of the rest. I have been sewing for years so I am no novice.

This is getting very frustrating my cheap old brother machine doesn't give me these problems. I have an expensive machine that is just a paperweight can you help me?