Displayed names of sharees changed automatically (i.e. local and/or shared calenders)

Recently I realized that the displayed name of sharees have changed to “personal_shared_by_” instead of the previous individual naming.

This happened in all connected Apps (Web, App on Mac, App on iOS). Surprinsingly it happened not for all users who are using the same instance. Is there an individual setting and if yes where to find it.

Yes, we made changes by upgrading our testsystem to NC 20.0.4. After more investigation I realized that the existing production system, still on NC 18.x has the same issue, all names of sharees are now “personal_shared_by_”.

The only thing in common is that Test and Prod are using the same LDAP Backend (MS-AD) for user sync/credentials

Any idea where to look or why this happend ?