Let's talk translation mistakes!
Everyone makes them (even native speakers!), especially on the first draft and particularly when there are deadlines involved.
The worst errors are the ones you don't catch, so let's go over how to find mistakes!

The easiest mistakes to spot come in the form of non sequiturs and logical inconsistencies. These are obvious from the English. Example: suddenly there's a sentence about fairies, but the story is based on everyday life and there's no mention of a fairy before or after

Sure, the author might be writing metaphorically, but it's more likely the せい came from the grammar ~のせいで rather than 妖精. Fixing these mistakes requires going back to the JP, but they can be spotted by the translator or editor (and less ideally by the reader)

Context is key. In a dramatic, very serious scene, the MC holds out a bag that "hangs like a bra"
This should be suspicious based on the tone, which isn't comedic at all. It's time to research the phrase ブラ下がる, which is a set phrase that comes from ブラブラ not ブラ

Let's be logical. A character says "Why did you put away the cleaning equipment?" You look at the panel and the cleaning supplies are clearly out on display. The dialogue logically doesn't make sense, so it's time to recheck the subjects and verbs

For manga, use the panels. You see the SFX ゴロゴロ overlaid on top of a cat. It's much more likely the feline is purring rather than rumbling ominously or tumbling along like a boulder (unless that's what the panel shows!)

Recognizing references matters too. A character is at a photobooth and the phrase チャリで来た pops up. There's no bikes around--did they really come by bike or are they referencing a meme? (Pixiv is a great place to look those up!)

Always, always look up waseigo. Does カンニング mean what you think it does? Does アバウト serve the same grammatical function in JP as it does in English?

When you come across a phrase you've misunderstood, you'll likely feel something is off. Listen to your instincts and start looking things up--when you figure something out, it'll be like a lightbulb has flashed on in your head

If you absolutely cannot figure things out, just ask for help! Try friends, translator communities, etc. If you have the money, you can even take JP lessons and review problematic passages with a native speaker (idea from @howtojapanese, see http://howtojaponese.com/2018/08/27/magnetic-lassos-and-other-translation-thoughts/)