I am facing a very annoying situation where I loose steps after 2-3h of work.
I have a 4 axes router, with the gantry being moved by 2 independent motors nema23, 3Nm.

One of the motors (Y) starts to loose steps, mostly after a period of work, 2-3h. Even though today when started the router, it lost steps for the first 3-4 very short runs (1-2min), then it went fine for the next 2-3h. The other motor (A) though is fine, no more than 0.05mm lost per 1h of work.

What i have tried so far:
- change the command of the motors, actually switch motor command pins between Y and A, and still y lost steps.
- checked the mechanical parts of Y, and all looks fine
- in the first 2h router can work at 6000mm/min on Y and A, but once starts to loose steps, even at 2500mm loses about 0.5mm (!!!) at a 5min run.
- checked the resistivity of both motors, and on all I have the 1.3ohm just like in the datasheet. SY60STH88-3008BF
- changed also with other bigger drives (EM806) but same effect.

So can it be that the Y motors is actually damaged even though it looks fine?
What i know is that a motor wither works or is damaged. Is that correct?

thanks
Marius