We were both wrong. I tried today again with my other Mac with Mavericks OS and got the error:82 again 
All I did was do the calibration again and at the first saving point I got the error again. Then I changed back to a Mac with High Sierra OS (10.13.6) a different laptop but same OSX version with which the error disappeared, and it disappeared again, no errors.
So it seems the error:82 is somehow related to using Mavericks OS (10.9.5) with Firefox 78.15.0esr, the errors are gone with High Sierra OS (10.13.6) with Firefox 115.10.0esr.
After calibration still more slack then I would like, even when i go up 50mm with the Z. I will keep repeating the calibration to see if it gets better.