I sewed a T-shirt dress for DD (twice I ripped out side seams and cut ti smaller after trying it on her) and when I got to the armholes the fabric got caught in the feed dogs, multiple threads wound around bobbin case. I cleared it all out and started again, thought the problem was the thin (same material) binding I was trying to sew close to the edge fraying. Happened 2 more times, so decided to do set-in sleeves, the shoulder seams sewed fine but still happened when I tried to sew sleeves in.

I've adjusted tension up and down, when too low the fabric gets pulled into the feed dogs but when higher I still get at least one (the longer I sew the more threads) thread cut and wrapped around the bobbin case, big loops on the underside of the fabric. I've tried it on scraps of the same fabric. What's causing this?