After looking through 10 pages of Stepper motor issues it seems my questions have been answered sparsely. It would be greatly appreciated if someone with insight into this problem would provide feedback for my next step to remedy this frustrating situation.

I have a used machine purchased from the manufacturer. The system came as a package about 3 years ago so no longer any warranty. Basically I have not had the opportunity to use the machine....3 parts built in plexiglass. I moved 2 years ago to take a new job and am just now getting back into using my tools.

The motors are rated at 5A the drive box has max output of 3.5A and is set for full step.
The Z-Axis helical/worm gear interface was so worn that i had to put a .220 spacer in the system to move the worm gear up the helical to get the slop out of the interface. I am now running at the max location the worm gear can be.

The Z-Axis loses position while running a program - in the first 6 steps of the program. After Z moves to the clearance plane for the XY movement and begins the first -Z movement it has no clue where it is. That is proven by sending it home and reading the difference in home on the readout...it is anywhere from 0.15 to .26 inches. Yes it is random.

X Axis does the same but not to the extent of Z.

Y was not doing anything wrong until Friday when it decided it would only make noise and not move the motor.

The motors were built in '99. They are Applied Motion Products P/N 5034-349D-005 2.5V 5A 1/2 Ohm

Applied Motion does not have any specs for them on their website. They are sending that to me.

The company that sold me this problem is willing to help me on the mechanical side of things but on the electonics side not so much. They want to sell me a new 8A driver box upgrade.

I am not an electronics guru.......as you may tell....much more mechanical. I am not sure what specific questions to ask to fix this set of issues. I have received great help here and thank you ahead of time for your questions and answers.