No issues on the XTR derailleur(s) here... I've heard people have issues, but I'm guessing must be batch related. I'm on 3 bikes with 180 days in the saddle across stable in 2020 and no issues on derailleur (nor on 2 bikes over 2019 season), purchase of the 3 derailleurs occurred between XTR release and March of last year so fairly spaced out. Hopefully it is a batch issue.
Agree on cassette, I'm blown away as my 10 speed and 11 speed XTR were like timex watches. The new XTR cassettes are like ninja stars after a season. Its nuts, all 3 were new in March 2020 and I'm wondering if a better option is SRAM or eThirteen... but swap from Microspline to Xd is a PITA.