[Machine Help] How to fix skipping stitches? Sewing Machines Parts and Sales in Los Angeles

I have a Singer Simple 2263, and lately it’s been skipping stitches. The weird thing about it, though, is that it only skips on zigzag or other more complex stitches. It has no problem with straight stitches, which means I can still use it at least, but it’s frustrating. It’s also not your standard skipped stitches in that instead of just leaving gaps, the zigzag will revert to a straight stitch and only zigzag about half the time. If there’s another name for this, I’d love to hear it!

The last time this happened, rethreading the machine fixed it, but I’ve rethreaded several times and it’s not helping. I also cleaned out the bobbin area and rethreaded the bobbin, but this isn’t helping either. I was out of sewing machine oil, so I didn’t oil it, but I will get some soon as well as some fresh needles.

My question is though, will this really help? And if it doesn’t work, what else can I do? I really can’t afford to take it to a repair shop right now, so any suggestions or fixes would be great. I’m trying to get a replacement manual from Singer since I lost mine, but I don’t remember it including anything about skipped stitches, and everything I’ve read online only suggests the fixes I’ve already tried.

Thanks in advance for your help, and sorry if this is covered in the wiki. I couldn’t find anything on it there.