I've had this issue too. I have a Bernina 730. Try the Isacord thread. My machine seems to like it the most. It's about $6 for a 1000m spool and can be purchased at your Bernina dealer. There are places to buy online too, much cheaper, but shipping is pricy. Once in awhile I still skip stitches (one, but never 5-6) but blamed that on me jerking or moving too fast. When I got my machine (I bought it used and it was shipped to me) it would skip stitches on a normal zig zag. It'd make the stitches on the left but not the right, of the other way around. ended up the needle was out of alignment to the bobbin. Kind of an odd thing, but you might have them check if you continue to have issues.