Just double check that the thread isn't popping out of the hook thing in the bobbin case. I find that mine does that sometimes which makes wonky stitches.

If your stitches are now normal perhaps you need a drop of oil somewhere?? Again, not familiar with your machine but noise generally equals lack of lubricant. If it's a 'self-oiling' machine it may just be time for a service. Check your manual even if it's supposed to be 'self oiling'. There may still be a couple of spots that need to be owner-serviced.

In a drop-in bobbin, sometimes the "bump" on the plastic bobbin case (on the right / front) gets a scratch on it. Then the thread gets caught on that scratched plastic. You can fix it by using a very fine sandpaper (about 400-500 grit). You only need to brush it with sandpaper about 3 or 4 times -- be very gentle. I see the damaged plastic bobbin cases a lot.

If that's not it, it could be that the bobbin case retainer needs to be adjusted. That's a simple fix that your sewing machine tech can do.

I would try (which I am sure have already done) and make sure your bobbin thread is threaded correctly and that the raceway is clear of debris.) The older I get, I have to check behind myself several times to reassure myself that I have, in fact, done it correctly.

FYI: I NEVER wind a bobbin at top speed.

Did you check online to see if there is a troubleshooting or FQ&A section on your machine?
I had trouble with my bobbin once and it turned out that a piece had broken off the shuttle.

I was so concerned of using oil on my self oiling machine. I put a drop on an old lid & applied a touch with a q-tip. My gosh it solved my noise problem. The bobbin is no longer jumping around. Thank you so much for your suggestion. [QUOTE=NJ Quilter;7756398]If your stitches are now normal perhaps you need a drop of oil somewhere?? Again, not familiar with your machine but noise generally equals lack of lubricant. If it's a 'self

Glad you solved your problem! Sometimes I have problems if I wind a bobbin on a machine other that the one I'm actually sewing with.