After update 12.0.2 to 12.0.4 contacts not longer accessible

After this update, no user is able to access its contacts. When opening the contacts app, there is a never ending spinning wheel. This behavior is for both existing users?

The database tables are ok and the contact tables are still filled with crypted blobs …

Is there a standard procedure to locate the error? Any chance to get my contacts back?

For the update I have used the web updater - it showed an error during the backup step. The I removed the maintenance mode and used occ for the update … then the update was OK.

Thanks in advance