We have updated Office 2019 to Version 2302 (Build 16130.20306) and the issue is fixed.
Update after new version (2023/03/20)
With the new version (Build 16130.20332), the files open again in Read-Only mode. The issue is back.
Update after latest update (2023/03/28)
With the new version Version 2303 (Build 16227.20212) the issue is fixed again.