Sarabela

I can sew straight lines with no trouble but when I FMQ the top thread continues to break. At one point I switched to a metal bobbin and things got better for a while but now is worse again. In doing some research I've found some comments that using too large of a thread spool can cause problems. I was using a 1000M spool so I switched to a 500M spool (maybe this is still too big? ) and it still happens. Should I try a thread stand? I also read that having the bobbin full can cause problems and to only fill it 2/3 full. I do notice that right before the thread breaks I hear a clanking nose in the bobbin area and the upper spool suddenly spins a couple of times causing slack between the spool and the first thread guide and it sometimes winds around the spool pin under the thread spool. The thread breaks at the final thread guide on the faceplate just before it goes down into the needle. Any help or ideas on things to try would be greatly appreciated! I've tried all the usual, lots of different kinds of needles, getting the tension just right, etc. I'm using Gutermann thread.