Trying to improve rpm consistency of this drive

[alank2]

I've been modifying a Sony MPF-920 3.5" floppy for retrocomputing, but its rpm is not consistent under heavy seeking.  I'll attach a picture of its control board.  On some older drives I noticed that the board that drive the motor/rpm was a separate board, maybe they did that to isolate it.  Anyway, under heavy seeking, the rpm on this drive speeds/slows enough to make it unfit for what I am trying.  Would adding a capacitor possibly smooth out the draw form the stepper?  Or perhaps the cap would be better on the motor power side.  Any other ideas?

Not a picture of my drive, but very close.