When I got my first 301 it had the same issue, it felt like it had a bind at the hand wheel end, and every so often it would skip stitches. I took everything apart, cleaned and oiled everything a few times to no avail. It was driving me crazy. Finally about the fourth time I was looking things over, I finally spotted a piece of clear nylon thread behind the bobbin case base. Some quality time with a pair of tweezers and I got about a half dozen little pieces of that clear thread out. All problems solved.
Cari