I have same machine,, occcasionally have same problems:
Try these ideas,, they have worked for me in the past at different times:
1 use dental floss & run it through the threading path,, sometimes there is lint buildup & causes thread to fray & break.
2 check the plate where the needle goes down,, I. Had a small burr from breaking a needle & it kept catching & breaking the thread. DH sanded it with fine sandpaaper, problem solved.
3 check that the thread is not hanging on, , caaught on spool or post. I find that if I use the netting it helps,, especially if using the horizontal spool.
4 I also find that moving sideways instead oof up & down seems to result in less needle breakage.
Hope these ideas help