I know this might not be my place, but if you help out with translating from English to Dutch I find very often that what is translated in ten words in English, is translated to one word in Dutch. I even found a sentence that was clearly translated by a search engine and copy pasted. If you don't like to much effort, stick to translating things with two words, please. Now everyone needs to do the same thing twice and maybe subtle diff don't seem to mean much in Dutch, they can be of cultural significance in Japanese or when you are building more complex sentences. There's a ton of info on word hippo for instance. We are all making sure other ppl can use Renshuu to learn a language. Sorry to come across so annoyed, but I sometimes take ten minutes to translate one word so to see ppl taking huge shortcuts makes me a bit angry tbh.
Without getting into too much data (which I unfortunately cannot do at the time), there's two main sources of data for Dutch (and most languages) - the original dictionary file that renshuu uses (JMDict) and user contributions. If it's the former, then it wasn't any particular user.
That being said, maybe adding an additional checkbox on the translation system to when you one is validating someone else's suggestions, then need to explicitly check a box saying "This covers all of the definitions in the original". Do you think that would help some?