Per ProZ guidelines, “points are (or should be) given to the most helpful answer, while the best possible term should be entered in the glossary, even if it was not suggested by the answerer who won the points.”
In principle, this is a beautiful concept. The person who provided the most helpful answer earns the points, even if his/her answer is not the most accurate. As ProZ explains,
Imagine for instance that you ask for a difficult technical term and get several similar alternatives, but one of the answers provided a very clear explanation that helped you understand the meaning of the term and its usage. Then you could pick another of the alternatives [for the Glossary], and still consider this the most helpful answer.
In our experience, though, we know that this is not always the case. Being a ProZ member for less than two months, I’ve seen discussions surrounding the topic. And I myself have witnessed cases in which the “most helpful” (meaning a mistranslation) became the “best possible” with no rhyme or reason. So, what to do when that happens?
First of all, you may post a polite discussion entry explaining why you disagree. Remember you are disagreeing with the translation that was entered into the KudoZ Glossary, not with the Asker’s right to choose the most helpful answer. It’s always a good idea to provide examples and references if you haven’t done so already. Your comment may not change a thing but at least it will be food for thought for another person searching for the translation of the term in question.
Another thing you could do is to use a different channel and submit a peer review instead. Technically, this is done by clicking Contribute to this entry next to the search term. However, as far as I can tell--and based on some discussions that I’ve seen, this feature is not working so you might want to report the issue to ProZ and ask them to fix it.
Finally, I strongly recommend that you create a personal glossary of problem terms that include the correct translation for the items you are in disagreement with. As you do so, remember to provide an explanation, one or more examples, and reliable references, if available. This will most likely make your translation more authoritative and will provide an alternative to the mistranslated term(s), thus enhancing the overall quality of the Glossary.