RT's have backlash just like any leadscrew system so its real important to back off X amount of degrees, approach the target angle from the same direction, with no putting in reverse along the way. If you have angular float in the table just sitting there, then I would suspect that worm gear has worn (assuming the ring gear teeth are in good shape & harder material). Now whether you can find or make that part, you'd have to investigate. It looks pretty good in the picture but hard to judge from here.
I think clamps are pretty important for RTs, hopefully something is out of adjustment on what look like clamp toe pads or can be re-made if worn. Or maybe the screws. When you first said no clamps I thought you meant the RT didn't have any period, but I think you mean they are there but don't function?
