How do you solve servo feedback error?

The question is not entirely clear, but I can think of two meanings:

1...All servos have a "follow-up error". This is the amount by which the slave fails to align itself with the master. This amount should be small, and is an inverse function of the system loop gain...ie: The greater the loop gain, the smaller the follow up error. The downside is that if the gain is too high, the servo may hunt or go unstable.

2...All servo systems use some sort of "tell-back" device, such as a synchro or sin/cos potentiometer, which reports the actual position of the slave so that it can be compared to the position of the master. If that device is inaccurate, then servo follow up errors will result. The cure is to use a more accurate (Probably more expensive) device.

If this is not what you wanted to know, please let me know.