Salut Sascha,
Thanks for reaching out!
I’m sorry, unfortunately I have no clue about this.
You can try updating the .po file from the .pot. If you are using PoEdit, the open your .po file and in the Catalog menu you should find an “Update from POT” options. Maybe the .po is out of date.
In case the .pot is out of date, then open that with PoEdit and choose Catalog > Update from sources.
I hope that will help fix the issue. If not, then the WooGuys are still your best bet.
Cheers,
Andras