Z malfunction?

I have been fighting printing issues the last 2 days (PETG/CF) seemingly getting progressively worse. Basically the first layer was perfect then it went down hill from there like it was under extruding I double checked all the calibrations and all were dead on. I came home tonight and threw on some PLA and the same thing happened. This time I noticed the Z was way higher than it was supposed to be on layer 5 when I killed it. Control said 1.1mm but it was actually 2.3mm. I checked the Z with a dial indicator right after and its dead on within .01mm from 0-30mm. I'm getting ready to change out the 8825 but can it be something else? I dont see anyway for this to be a mechanical issue. both Z motors run off one driver so I doubt its the motors as they appear to be synced. 1.4/Arduino 2560 BTW

Edited 2 time(s). Last edit at 02/20/2018 07:54PM by Bill Clark.

The problem is solved. The error appears to have occurred during Z lift while retracting and accumulated. A new driver eliminated the issue but that may be because of a slight change mechanically or electronically that caused the original to,after 3 years perform differently.

I'd check the microstepping-jumpers under the Z-driver for good contact.
Also worth looking for are the leadscrews and nuts. They don't live forever, especially the part of the leadscrews at the bottom. ( you can turn them around once )

I'll bet your right about the lead screws. this thing has a lot of hours on it, something changed. Probably increased friction from wear.