Mine does this occasionally - for some reason ever once in a while it pops out of the little spring wire that takes up that tiny bit more of slack from the uptake lever. I have yet to figure out how it happens as with my machine, it's darn near impossible - but it happens. When that little bit of slack does not get pulled up, when the needle goes down it loops wrong and the hook grabs wrong.

I've found if I add an extra loop to the upper thread path, that helps keep a bit more tension on the thread and does help. I run it from one spool holder loop to a second spool holder loop and then to the machine - or if on the machine, to a spool holder loop and then back to the machine.

Longarms have a lot of problems with thread as they sew very fast - and use a lot more thread holders between the spool and the tension to keep loops that form as the thread whips around from getting pulled into the tension and messing things up.

skipped stitches is often caused by the needle

Take the stitch plate off and double check that there isn't a piece of thread stuck in there, either from a bad cut or a broken thread.

I had a similar and it was a real pain as I was using poly clear thread. Try to find that in the feed dogs.

I agree with Tartan since we both have a Bernina. This happens just occasionally to me too. I just re-thread and continue quilting.

Superior needles are Organ.

I can see in your photo, that your needle thread is twisted around the needle shaft.....Check threading and that your threadsin the take up lever.

I agree it has to be in the way it is threaded or the placing of the bobbin. If it is happening on two machines it indicates I am doing something incorrect. Although it is a vintage machine, my machine calls for the bobbin to be placed where the thread is coming off in 1 direction. If I reverse it, it won't sew correctly.

It is probably backlash . Tighten up the tension spring on your bobbin and maybe put a small paper disc kind of like a washer beneath your bobbin.

I have also seen it when the foot lever is not lowered all the way to the fabric you are sewing.

My machine doesn't like a certain bobbin that is supposed to be for that machine. Or your bobbin may have been bent or stepped on.