I have a Bernina and had the same skipped stitch problem when I made a Bali bag. I rethreaded and changed needles like crazy, but it didn't solve the problem. After much searching, I found that one of the causes can be that the needle was not heavy enough for what I was sewing. Changed my needle to a larger size (18 I think) and that solved my problem. Maybe my smaller needle was bending because I was sewing through so many layers -- whatever, it worked for me.