I to am having the same jumpy problem at low speeds with my X axis using the 4 axis Mechatronics board.
I switched from a Xylotex 4 axis board that ran fine until a lack of proper grounding on my plasma cutter messed it up some how.
The Mechatronics board has a lot of good features so I’m hoping some how we can figure this out. I look forward to watching this forum post

Dzackman

Solved my problem, it was a loose wire. For anyone else with the motor jitters at low speed, check and check again your wiring.

Dzackman