Document library (preview) modern webpart goes blank when grouping by

I have the same problem.

It is equal which browser I use.

When you open a part of the group some fields are empty:

When you click on the group to filter the view then all fields are shown:

Back to the grouped view the fields are shown.

But only from the one Group:

I have opened a case at Microsoft and they are working on the case since a month.

The first workaround since Microsoft is set the grouped view to extend and not to reduced – this works but don’t helps me.

In the moment an escalation engineer is working on the problem – but they said the process takes a few month (!) to solve ☹