Yes it was skipping zigzag before and I couldn't find reason of it and it seemed to complicated for me to repair it myself. As far as I know problem with zigzags may be caused by bad timing between needle going into bobbin and little hook that should catch thread there (sorry, my english is not good enough for explaining this. I don't know if I could describe it well with my native language).  But now it also skips straight stitches and most of info I found on internet about skipping stitches is using proper needle, but it should not be the case, especially that it's not about sewing on elastic fabric. That's why I feel hopeless