Hi! I‘m trying to sew using my moms old Kenmore model 158.1789280 machine, but neither of us have had any luck getting it to do any stitch other than a straight stitch. I opened up the top to look at the mechanism, but I know little to nothing about how to fix it (or even just what to look for). The inner workings themselves all seem to be well oiled, so I was wondering if anyone could offer some possible solutions.