Check your idler bearings. You can mark them with a sharpie for visibility and give them a spin.
Check the motors themselves. If a small gap is not applied when tightening the grub screws, the gears can bind against the motors.
The belt could be out-of-spec, try using my 6mm belt splitter on Printables.
Check all the shims that are supposed to be there are present.
Check that all the idlers are tight; loose idlers can bend and rub the surface they sit on.
Lemontron Rev E; After some time, the plastic in the carriage block can drift, needing retightening, but if you retighten enough, it’s just “dishing” the medium shim which will ultimately bind the idler. For mine I used ABS, and this fixed the issue compared to my previous PETG one.
