Looks a lot like my Juki8700. I'm going to assume it's taking round shank needles so you have to be very careful that you are getting the needle in with the hole centered correctly. It's one of the things I dislike but understand why it's done that way. My husband has no trouble, but with my stigmatism I don't see real "straight" to start with so it gets harder for me to do (if I look down a straight 2x4, it will appear to have a curve in it)
I have not tried to do any FMQ on mine as I own an LA. However if it was working until you removed the feed dogs, you may need to lower the presser foot bar so the foot is riding slightly lower and putting a bit more tension on the fabric. However that issue normally shows up as skipped stitches and less often as thread shredding.
This sounds more like a timing issue, and it's possible you will have to tweak that after the other changes as now the fabric tension is different. I don't remember which way to do it, but you can alight the needle hole up slightly off center and see if that does it. That effectively changes the timing slightly.
Last edited by Macybaby; 05-23-2019 at 06:19 AM.