a) An individual level leaderboard displays something like "1.1 - score - Normal" at the top, while the "score" part is always in lowercase independent of its translation. This also applies for the wave leaderboard page.
b) Some languages use the period and comma in numbers in the exact opposite way than English does it. Due to this barely being handled the numbers are displayed wrong in almost all parts of the game.
c) Some strings seem to be completely missing and are always displayed in English, for example in the Screen and Debugging section in the settings.