Dual extruder calibration print repeatedly shifts towards x-Axis during print

I have tried the DSE calibration print three times now. Whilst generally the calibration seems to work (pretty much aligned parts), everytime during the print at seemlingy random moments, the entire print shifts 0.5 - 1 cm towards the X- Axis and therefore making the print useless. I can definitely rule out that the flexblade is moving or the print was moving on the printbed.

I have redownloaded, resliced and used a different high quality SD Card I usally use for my DSR- Camera but the problem pertains.

Any Ideas what could be the reason and how to fix it? I never had this behaviour with single extruder prints so far so it must have to do with re-locating the starting point after hotend switches.