Machine off at the end of the programm. Repeatable!

Consistent position errors after a long program could indicate a step timing
or polarity issue. Too low direction setup or hold times could cause a lost step
at reversals. Wrong step polarity can also cause this issue as stepping on the
trailing edge of the step pulse (rather then the expected leading edge) will
decrease the expected hold time.

It might be worth either inverting the step polarity or increasing the setup/hold times,
at least to see if it changes anything.

unknown wrote:

Some of the cheaper fixed bearing blocks are sold with non angular contact bearings, this is something to check.
Until you perform a backlash test, and yes this can manifest as repeatable, you can not rule out a mechanical issue.
 

I machined the fixed bearings myself. You can find the parts on cults, the bearing has proper angular contact bearings and the mechanical play is minimal. Keep in mind the pictures are with the old couplings!   cults3d.com/en/3d-model/various/y-achse-kus-frasteile

Let me know how exactly you want me to perform the backlash test and I will give that a try. 

PCW wrote:

Consistent position errors after a long program could indicate a step timing
or polarity issue. Too low direction setup or hold times could cause a lost step
at reversals. Wrong step polarity can also cause this issue as stepping on the
trailing edge of the step pulse (rather then the expected leading edge) will
decrease the expected hold time.

It might be worth either inverting the step polarity or increasing the setup/hold times,
at least to see if it changes anything.
 

Polarity could very well be an issue! I changed a few things on the control unit recently and did not pay close attention to the polarity. I thought that would not matter. I will test that asap and report back.