Changed my belts. And whoaah, they were stretched. A part that should have been 57mm came out at 61mm. Now I'm back to sane part sizes. It has also helped a little with the banding, but still not great.
FWIW, I recently tied down the x-motor to the vertical post with cable ties to stop it from tilting in the mount, and the ringing got a lot better. Just don't forget to place shims behind it to keep it at a right angle, I used 2mm thick shims.