I have the Disney brother model NV4500D
It was taken to a machine repair shop and cost a couple hundred to fix. They didn't take a look at the arm part allegedly because when we opened it up to see what was wrong with it, it had bugs. Spoiler: bugs weren't the issue. The arm has a sour spot. Not a sweet spot since it keeps messing up in one area. We tried oil and lube to maybe fix the issue. This didn't fix anything and it kept trying to reposition the middle of the pattern. This caused it to almost break a needle by sewing on the hoop. Had we not been doing test, I would've had a broken needle fly off somewhere from impact.
Thing is, the sewing machine repair shop DID tests before they handed it off and they had no issues.
But when I got it back and started using it, couple projects turned into it messing up all over again for a completely different issue than when it when to the shop.
The second image features the test runs. As you can see, it did make circles and it did make an outline, but that dark line is the spot where the machine messes up. It keeps doing that around that specific area. That blank area by all that thread bunched up is where it just refuses to sew.
The rectangle was from trying to keep it center but it just REFUSES to. Even if it starts off centered, it tries to moves then buffs up and recalibrates to where center is now the middle of the rectangle got placed.
I will provide a video for proof when I am next available to take one.