May sound obvious but if you are using pulleys are they the same size.?

If this was Step/Dir setup I'd say the Step pulse was on wrong edge but with Analog IP-A then can't happen.

Does it look like it's running out over time while cutting or is it off straight away.? . . . . It could easily be electrical noise inducing voltage on the signal lines.
This would have the same affect has being told to move fractions of inch more than should. The encoders will always bring it back to zero when homing so very difficult to see.

Does it do it without Spindle Running.?
Do you have any Line filters on the Drives or VFD.? . . . If not fit some because Servo's, esp Analog don't tolerate noise in power line very well.!