Margaret,
Use a back light, turn the hand wheel till the feed dogs are all the way up. Then lower the presser foot and sight along the sides of the foot and the edges of the feed dogs. They should be parallel on both sides. If the foot is turned one way or the other, the fabric will turn and twist as it feeds.
I've lost count of the number of feet I've had to adjust to fix a twisting fabric problem.
The best bobbins I've bought have come from Sew-Classic. They also have good quality bobbin cases too.
Joe