Bug Reimport stucked when upgrading from 2019.3 to 2019.4

Hello,

I have a problem with upgrading a project from Unity 2019.3.13f1 to Unity 2019.4.0f1.
It's reimporting all assets since hours.
From what I can see above the progress bar what currently gets reimported, it's stucked in a loop for the packages like "unity.com.shadergraph" and other packages looping through all scripts over and over again.

Now what should I do? I assume if you cancel the upgrade progress, the entire project gets corrupted. Not sure how many hours I still should wait until it's finished.

Furthermore, on another project, I also tried to upgrade but my PC shut down after some progress. There was no OS update or other planned shut down during that moment.

 

Small update: The update progress has now stopped at the file you see in the attached screenshot.
Now in task manager Unity is reported as "Not responding". I guess the update process has freezed and failed.