Maybe I should also start printing from SD Card. It' s just funny because it used to work without problems.
I doubt that it has todo with my laptops CPU because it used to run fine on 16.04 on my current laptop (where the CPU max while printing is 5%) and also used to run fine on a much older laptop with all Kubuntu Version running back to 2012.
Probably there was some change in the new Linux Kernel version regarding the USB stack.
Btw the reason for the circling was rather out of sheer stupidity, I fiddled around with Cool...