Sometimes translations prepared by professional translators are reviewed post-delivery by client organization personnel.
Our company’s standard translation services already include post-translation proofreading by a second linguist for all projects. When clients assign internal personnel to review a prepared translation it’s a third or even fourth review. At this stage detection of a translation error is unlikely. More likely is an internal reviewer might notice a translation word choice that deviates from a client preference or recognized industry word usage. In this case a modification to the translation to conform to a preferred word choice or terminology can be an improvement to the translation.
Often though reviewers are not given sufficient instruction or narrowly tasked. Instead they’re handed a translation with the question “what do you think?” In this scenario there is almost an implicit request that the reviewer is expected to make changes to the translation to “make it better” somehow, whether needed or not. In some cases reviewers may completely re-do the translation prepared by professional linguists, begging the question why were professionals hired for the project in the first place?
In our experience reviewers of translations are of greatest value if they are asked to review a translation for general readability and only if they notice something that is of high priority to adjust should they make a change. Otherwise the work and judgment of professional linguists should remain in place. That is after all what was purchased by the client … the professional language judgment of the assigned translators.