Wow, that's an odd place to twist up. Usually that's under so much pressure and tension that it won't twist there. So under regular sewing it will just twist up and then of course break the thread? You sure it's not the thread shredding and then forming a ball on the next guide? What thread are you using? And have you tried other threads? By the time it gets to that point it should have worked out any severe twisting, there will always be a little but nothing to spin it up to break the thread.