Invalid byte sequence in utf-8 Zammad Software

Question

Hi there Stackoverflow Community,

I've installed the Zammad software recentily and I want to import some User-Data, but the "invalid byte sequence in utf-8" error message appears. When trying to configurate S/mime i get the same error message :/

I'm not too expirienced but i think it is an encoding issue and has to do with a locale configuration.

root@h123455:~# locale -a C C.UTF-8 de_DE.utf8 POSIX

Infos:

Used Zammad version: 5.1.x Installation method (source, package, ..): package Operating system: Debian 10 Database + version: postgresql 13 Elasticsearch version: elasticsearch 7.14 Browser + version: Firefox99.0.1

Is there something missing at the local configuration? I appreciate every hint you can give me to solve this problem :)