Thank you Sineos! This was a very helpful hint. I changed the strategy for fighting the issue and started to optimize the retraction amount. With a bit less flow it was possible to minimize the retraction to a minimum of 1.25 mm. I think the printer is minimal under extruding now, but as the results are still excellent this is no concern.
Do you think if the minimum measured retraction is 1.25 mm to set the retraction to 1.5 mm also for other PLA filaments?
This printer is used by many people, and it is a very hard task to communicate that they need to change settings on every filament change. So I need to use universal settings even if it means that the quality will be slightly decreased.
Yes, reading and understanding the code and the math taking time, which I actually don’t have. But I there will be no way around this in long term. I’m a good low level programmer and did write some very efficient stepper driver using DMA and perfect timing with minimal CPU usage for some architectures. But I think understanding the Python and Math in klipper will be a bigger deal for me.
I did a lot of prints in the meantime and I had no problems or unexpected side effects. Maybe a slightly slower print. So for the current version, klipper has handled the delay fine, it seems to be safe to use or at least to test my little hack, if somebody has a similar issue.
Of course, I stopped using it now.
Thank you for your help and time, it helped me out by tracking the issue.