After returning from a long vacation it was time to do some work with the Voltera again.
The machine strugled with measuring the probe and threw a few errors, but suddently worked. All looked good until I tried to dispense solder paste, everything was offset a millimeter in the X axis.
Inspecting the calibration microswitches I notices a small lump of old hardened solder paste on one of them, that explained the offset. Carefully cleaning this made all the difference.
I now inspect and clean up any small spills every time I finish up (a lot easier when it's still liquid form).