... I would recommend that you report it on github.
https://github.com/osTicket/osTicket-1.8
No 1.9 reporting on github available yet.
Same problem here with the 1.9.4 - rc5.
Did a fresh install with english only. Then added the german pack and all got scrambled.
Did a "partial" reinstall by dropping all ost_ tables, resetting the config to "not installed" and using the already existent files on the server. Still scrambling of the extra characters (see attached image)Red = wrong display, Green = correctly displayed