Heyy I have had my lulzbot taz 6 for almost 5 years and in the last 2 months it has become unusable because of the bed jerking around I have replaced the stepper motor, belt and bearings with no improvement at all. This happens no matter how big or small the print is and it also doesn’t matter if I’m printing from and sd card or a computer I use lulzbot cura as a slicer
Sounds like stepper driver if you’ve replaced the motor, belt and bearings properly without any effect.
As is software or hardware drivers
The physical stepper drivers on the motherboard.