It's possible that the needle is flexing slightly as you sew because it's being pulled by the fabric, making it impossible for it to form a stitch. Use a needle that's more rigid and be sure you're not moving the fabric too quickly.

Mine skipped when I tried to quilt a T shirt quilt. The only 'fix' for it was using a topstitching needle.

Re needle changes ... remember it's not just about putting in a new needle, but often times, it's a matter of changing the type of needle and the size.

My go-to FMQ needle is Embroidery 14 .... not that, that is always where I stay, but is where I start, and then branch out from there to other sizes or types, according to how things work out. (or not!) :)

Thanks everyone for the suggestions! I was up til 3am determined to find out what the problem was! I had tried various size needles.. Went back to the 90/ ballpoint seemed to work the best but still dreaded skipped stitches!! GRRR I finally turned the tension to 5 which was never used that high before, figured my thread would break but no, and it worked pretty good! Haven't been back to tackle it yet today, hoping I can finish it! I don't have any quilt shops or repair anywhere near me unfortunately or I would of taken it weeks ago! Ugh

Why are you using a ballpoint?? Those are designed for knit fabrics and are rounded so the tip pushes between threads. This might be contributing to the problem, especially if the tighter woven fabric is impeding the timing of the needle as it pushes through.

When I'm FMQ on my domestic, I use a 16 or 18 topstitch. A topstitch needle has a larger eye and a longer scarf. The scarf is an indentation in the needle that the thread tucks into, which protects the thread from the friction that occurs as the needle moves in and out of the fabric.

Peggi I don't know why I said ballpoint, just looked and it's a Schmitz microtex 90/14 that I put in and with increasing the tention it was doing better! I stitched but didn't finish but I will today if all goes well:/ I'm using aurifil thread and
In bobbin.

I suspect it is your needle......try a 90/14 topstitch. Sometimes, due to batting being thick and the movement of FMQ, the needle and bobbin thread don'the "lock"....if the needle hole is larger, the thread will go through better. Also, use 50 weight thread.....it is thinner and makes for smoother stitches.

UPDATE: it's doing better with the 90/14 needle and tension is on a 5! Never used it that high!! Much better but still
An occasional long skipped stitch and that is with me going a slow speed! I'm going to try other needles as suggested,
I have been using 50 weight thread... Maybe I should try a different thread as well.. Not giving up yet!!

Long shot but it worked for me. If you use a plastic bobbin, replace it with a metal bobbin. Nothing I did stopped all of a sudden skipped stitches on my Brother 420. A late night internet search found a machine tech that said use a metal bobbin not the plastic one. I changed to a metal one and no more skipped stitches no matter what thread or needle size I use now.

I didn't know you could use a metal bobbin on a brother machine! I have only seen plastic! I have several metal ones for my vintage machines... If I can find one the same size I will try! Thanks!