I still have my pe180 and pe200 and I understand that your square is a built in design that cannot be deleted! I never had that problem but I’m going to suggest that perhaps you are putting the bobbin in wrong. Though actually, I’m wondering if the emb arm has been bumped out of alignment. There is a downloadable "repair/service" manual that details with pictures how to disassemble. I’ve done so several times in the past, removing the arm and cover when the needle needed timing. If these suggestions don’t help, it could be that the memory board has failed for this particular design. Last resort…stop using that design or seek professional diagnosis. These little early machines are truly work horses, and give few problems. If you cannot d/l the service manual anymore from Brother support, I’m happy to pdf you a copy. Hope you get it figured out!