The drive plates when spinning very fast cause a gyro effect. if it wobbles on its own without you holding it then you have caused the plates inside to shift and the gryo is destabilized. if you hold it and it doesnt woble till you apply force your plates are fine.

the larger capacity drives are not very well made and are very sensitive to shock.

i would say dig out your reciept and return the drive under warranty or replace it with a differant drive