I have been battling this for some time now. The prints come out uneven, wavy and just overall shit.
The resonance is terrible as well.
What i did:
I have changed the belts to try and fix this, have the back metal motor plates, to access everything.
I even fixed the belts snagging on pulleys.
The printhead was reprinted along with x rail holders on both sides as they were falling apart. They are as solid as rocks.
Tried various speeds, accels and resonance profiles.
The printer is mechanically sound, bed very straight.
Honorable.mentions:
When doing the resonance testing I clearly hear rattling sounds. I have checked everything, all screws tight. The only thing that could rattle is the x carriage. The small vibrations are also there when moving the printhead very slowly by hand. Can be heard in the video.
What can it be? Should I change the carriages?
I don't thing that could be anything near the motors as the sound moves along with the printhead.