Exchange 2016 - Localisation broken after disaster recovery

Hi,

A month ago we had a critical failure on our server and needed to do a disaster recovery.

I set up a new Server with the same SW-Version and re-mounted the old database and most things work for now.

But our localisation seems to be broken:

Our ECP is now suddenly in english. This didn't have high priority for me, but now new accounts are automatically localized in english - while being setup as german.

Get-Culture

LCID Name DisplayName
---- ---- -----------
1031 de-DE Deutsch (Deutschland)

>Get-MailboxRegionalConfiguration -identity Administrator

Identity Language DateFormat TimeFormat TimeZone
-------- -------- ---------- ---------- --------
[redacted]/MyB... de-DE dd.MM.yyyy HH:mm W. Europe Standard Time

I tried to run this prompt for changing a new shared mailbox I was setting up:

set-MailboxRegionalConfiguration -id "54383a39-9ca8-4d19-b485-1c443eda3262" -LocalizeDefaultFolderName:$true -Language de-de -DateFormat dd.MM.yyyy

 but even after  runningOutlook.exe /resetfoldernames the foldernames stay english (inbox instead of "Posteingang").

Is there a way to check / repair the translations?

I encountered on error when I was starting the exchange management shell, no idea if this is connected:

Show quick reference guide: QuickRef
Exchange tips file C:\Program Files\Microsoft\Exchange Server\V15\bin\\en\extips.xml not found!