Hi fedthanshamann-6234,
I see the same behavior -- you've got group writeback turned on in Azure AD Connect. It doesn't writeback the names, just the GUIDs and the memberships.
I assume this is a safety feature to prevent group name collisions -- actual names write into the Description field of the group. Check the user's memberships via your tenant's admin panel rather than ADUC and it should show the group memberships with names rather than GUIDs.
So as far as I know this is working as intended, nothing to worry about.
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