Application language
I live in the Czech Republic so have a czech IP and have British/American English, Czech and Hungarian languages installed but my system should be primarily British English. I have had problems with a few applications opening in Czech. I first noticed in terminator - I run a command and the CLI replies in Czech. This stopped recently, I did add EXPORT LANG=C to .bashrc while troubleshooting. I have checked my locales and it looks all en_gb, I can't figure out why some things are in Czech.
VLC is one, I installed through pacman and it launches in Czech, I recently tried launching it from terminator and it opened in english but if I launch from the application menu or by double clicking a video in Dolphin, it opens in Czech. I tried another media player later and that runs in czech too.