Two heads are better than one
Errors can occur, especially when you work with thousands of words on a daily basis. This is the case, for example, with translation. It is a human activity and therefore not exempt from mistakes.
Mistakes can be hard to find after long hours working on a text. Consequently, high-quality results require revision from another professional, who will easily spot potential errors.
As an editor, my priority is to identify those potential errors, making the appropriate amendments so that the translated text keeps the original message and is consistent and correct in every sense.