After printing several parts okay I noticed that my whole prints were slightly tilted to the left on the X axis. This was very strange because I did not change anything and kept the rod lubricated all the time.
So I went through all the parts that affected the X axis.
Finally I noticed that there was a little abrasion on X axis belt’s side facing towards me. I think because I CA glued the belt to the extruder mount (stone me to death. I did deserve it !) not totally in line with the bearing assembly, the acrylic washers touch the belt.
Some time ago I detected this already and lubricated it but forgot about it.
There are two options to fix this.
After lubricating the acrylic washer in the bearing assembly the first half of the print went ok but the top half (as shown in the picture below) still kinda shift-warped left-right. So this is not a solution.
2) New extruder
By installing a new printed extruder I could get rid of the misaligned belt-holder-on-extruder and the bearing assembly.
3) Aligning belt to motor/bearing assembly
In the picture below you can see how the layers all shifted to the left. The black line devides the unlubricated print (bottom) from the lubricated print (top)