Looks like a heavy workpiece and a light rotary. Might be just a little backlash in the rotary so first thing I would try is to rotate the the workpiece one way or the other so rollers pre-loaded. Slow down the acceleration some more. (Bigger number) Maybe turn off “Return to start” and run it once with 0 power, or could probably do it by hand, just take up any slack. That MIGHT be the problem. Like I said I’m not a roller rotary guy. Have a big rotary table, 2 different chuck type rotaries, and a linear table but no rollers. On the big rotary table I have ran into backlash issues due to a lot of rotating mass working the setscrew loose.
I need to etch on ranging from Ø.866 down to Ø.484.
You might be better off getting a chuck rotary. Repeat marking is not measurement dependent, only have to mess with focus.