We have found the root cause. As of release 1909 there is a new better globalization experience for message templates:
From the release notes we have: *Templates now provides a better globalization experience. With the new system,
admins using message templates only see templates for the active language. For
example, if an admin uses the Workspace ONE UEM console with Japanese, they
will only see Japanese message templates.*
Some of our templates have not all needed languages added in the list. That's why if Organization Unit language was not on the message templates list , global template (generic one) was sent.
We added almost all languages in the templates, and we configured them
Fix done! 🙂