Yes, everything is set to ANSI.

I figured it out. Best mistake ever

Alright: I deactivated the cache files in the database driver (since its annoying to manually delete them when someone else changes the database and puts the changes into the repository).
BUT: I only deactivated the cache files in the 64bit version of the driver config. And since we can't update to 64bit (because of the security library which does not support that one WIN32-/CNG-API call) I switched back to 32 bit... and completely forgot to delete the CCH-files (or change the other config file as well).

And since I was sure I deactivated the CCH files I did not check nor delete them.

Interesting that it only affected the Text fields and not the ASCII ones...

Sorry for wasting your time and thanks for the valuable input.