This can go both ways whether you understand both the original dub and the subtitle language that differs from the dub, for example: I recall watching a TV show episode where a conversation about a friend of theirs being drafted to war, but this piece of dialog was horribly translated: “He’s still a kid” as in the guy is his early 20s.
The subtitles in 日本語 however, used the worst wording for this idiomatic prasing by translating “kid” as in a literal minor (子供) when the real context is more on referring to someone who’s 20 years old or above (basically equivallent to saying “young man” / 若い人) which butchered the scene since the subtitles failed to express that.
I mean, do you know examples of a movie or TV show where the subtitles suck at translating the spoken dialog when it involves idioms, puns or even cultural references? Whether it’s French Dub & English Sub or vice versa (like English Dub > Spanish Sub & etc.) since each language has their own way of conveying a message.
I’m from Finland and usually the subtitles for English content are good.
One challenging example that comes to mind is Baby Shower. Since this concept is mainly from the US, there isn’t an equivalent term in many languages. People here usually just use its English term, but I’ve seen subtitlers sometimes translate it as vauvasuihku, which literally means “baby shower”, but no one is going to understand that term.
In one series, there was the phrase “What is this, my shower?”, when a pregnant woman was asked if she had already chosen a name for the baby. The subtitler had translated this literally as Mikä on tämä suihkuni? (≈What is this shower of mine?), completely losing the context.