You can rename the /text_de/ and start the game to see if it’s an issue with Full Rainbow.
If you’re having issues like this report you have your answer:
[1.3.0.4.] German Translation
If more tags are missing and I assume you got the single-file from the Website. However, if you’re still using the files from GitHub and you have at least AoM - download the file from the Website:
[Tool] Rainbow Filter (Item Highlighting) - #944 by WareBare
with that file make sure neither location where the files can go has any old Rainbow Files.
You won’t have to update it as much, that’s the good thing about the one-file approach. Unless AoM gets an Achievements update, it won’t cause any missing tags.