First of all, those who kindly translated the PJ files were amateurs and volunteers. Those who did the interpreting were paid professionals.
Secondly, both jobs involve interpreting what was said or written so it makes sense. Google translate doesn't do that very well, so you can see the difference. That's why two different translators may give slightly different interpretations.
They would have been paid, but it's not clear whether they were professional interpreters or not. Murat certainly wasn't (although no one seems to have had a complaint about a misunderstanding in his case).
My issue is that I, for one, have no idea how competent the lady was who intepreted Gerry's statement on 4 May. Perhaps she was, or perhaps she was just the first person who was available at short notice with a working knowledge of basic English, until things got a bit more organised.
IMO, some people seem to attach a huge amount of importance to the supposed discrepancies without taking into consideration the possibility that it was just a lost-in-translation/ confusion issue, which got rectified at the next interview anyway. Whether that's the case or not, perhaps we'll never know.