Diagnosing bad motor/driver. Vibration at low speed

[threedee]

Hello people.

Finally started rebuilding my laser bit by bit, after getting fed up with sellers warranty fix promises.
Today is X axis stepper/driver's turn, as rebuilding X axis.

I'm having moving resonance issues in toolpath. Someone suggested to run a project and keep hand on the head as its moving (dont worry, laser tube was off :D ). I noticed pretty strong vibration in X direction while accellerating/decellerating and on constant low speed (10-30mms).

Before i had been advised to swap over drivers to see if other problem goes away or moves to other axis (X overheating with a lot of small acc/dec movement). It didnt. Drivers function.

Question is are they functioning correctly ? Or is the motor flaky ? Do stepper motors go flaky ? Not outright dead but weird, ghosts'n'stuff?

As for drive spec - no clue. M415DRV. Unidentifiable. Current set to 0.57A RMS. Stepping X32.
Motor is 17HA705Y-1A, FH171215 Smooth, 34mm nema17. Again, unidentifiable.

Any way to diagnose this without outright replacing motor and driver ? (which i dont have spares of).

#Edit# P.S. I cant seem to disconnect the "connector" on the motor. Is it just a piece of plastic and wires are just there ?