Or when the character is bilingual but the subtitle just says: [speaking a foreign language]

On subtitles - when the person on screen literally says a word in english but the subtitles replace it with another word.

Depending on the word, this is actually sensible since borrowings tend to change the meaning of the words being borrowed.

A silly example of that is the Japanese garaigo "ダッチワイフ" datchiwaifu. It's a borrowing from English "Dutch wife", and recognisable as such... but you definitively don't want to translate it as such, as in Japanese it conveys "sex doll".

ivxferre is right, so I'll just state of a few examples:

Baito, which in fact comes from the German arbeit and means a part time job.

Apiiru, which comes from the English appeal but actually means to emphasize or play up something as a way of making yourself more attractive or making a point. For example, you can say "He looks like a good guy but that's all apiiru".

Cureemu, which is supposed to be the English claim but refers to complaints or having an issue with something in general.

I'm actually fine if the subtitles have to be truncated to communicate the same meaning in less space.

I actually find it harder to comprehend the subtitles when someone tries to be as accurate as possible, especially if the subs transcribe every little stuttering. I'm here to learn the stuff they people on screen are trying to say, I'm not interested in the subtitler's scholarly digression into the finer points of what they're hearing.

Some person in reddit once did a hilarious thing where they whipped out a full blown IPA transcript and started analysing the finer dialectual points of a viral video, trying to pinpoint the origin of the speaker. It was hilarious. Probably even more hilarious to linguists. But the point is, that whole thing was not what we were there for, we were just discussing a viral video.