It sounds like they don't have to translate, already done.
That said, my view is that while I very much appreciate the effort of the volunteers involved, the Viki translations are done under a lot of time pressure, and by amateurs, and at times it really shows.
I also really hate the fact on principle that Viki don't pay their translators!
That said, the Viki team certainly made a great job on making these shows accessible, and do an especially good job when it comes to to things like explaining some of cultural context, jokes and references, which some other subtitlers (such as Netflix) annoyingly tend to just ignore (or assume Westerners won't get) altogether.
But there are certainly mistakes, albeit mostly minor, in Viki's s1 subtitles (such as missing context such as translating references to Princess Royal as to 'his majesty' etc etc). The issue for me though is not really about mistakes, more about the fluency of the translation, and personally I'm finding the versions on the Special Edition a bit of an improvement in terms of terminology Westerners are more used to (and at times just sticking to the chinese is a better option).
There are also a lot of minor things - when Fan Xian comments on Guo Bao's poem for example, the Viki trans is 'The intonation is wrong', which seems to be technically correct, but unenlightening to me at least. The SE version makes it clear saying 'The falling and rising tones don't match', which now that I know something about Chinese poetry rules, is very clear. Similarly, the translations of the poems seem better (though translation of poems is incredibly difficult and controversial I know!) - the Du Fu poem in the SE version for example makes the lines rhyme (not quite managing the original pattern, but at least hinting at it), which I really like, and also is worded in a way that makes the reasons for which lines were assigned to which speakers a bit more obvious (the most obvious being the Emperor ...alone on this height) - though I have to admit that it maybe just rewatching that scene another time I realised the significance of the various assignments more!