I guess my view is a little different as I find it important to try to bear in mind the context.
It was all hands on deck on Thursday night in a village. The urgency for the GNR and later the PJ was to try to understand what had happened.
Contrary to the idea propagated that everyone in the Algarve speaks English, none of the officers present from police force seemed to have done (unless there is an exception that I can't recall at the moment).
Silvia must speak reasonable English and was no doubt trying to do her best, even if she may have sometimes misunderstood a bunch of panic-stricken Brits, some of whom have regional accents, speaking in colloquial English that aren't always easy to understand for non-native English speakers.
In the circumstances of that evening, I don't find it reasonable to expect local police forces to hire professional interpreters, nor do I find that it would have been expedient.
Concerning the initial statements at the PJ station on 4 May, as far as I recall, the PJ officers taking those statements were not those in PdL that night. If that's the case, they wouldn't have been familiar with, e.g., the layout of the apartment and is quite likely to have been taking notes or drawings as a visual aid.
From the sound of various descriptions, the station didn't initially seem to have many resources at hand.
They had to quickly find someone who could help interpret at short notice, which they did. I have no what experience this lady had. Was she a professional interpreter, translator, a private contact who could help out?
I'm sure that she was trying her best as well, but she may have faced the same language difficulties as Silvia had, with the additional disadvantage of not knowing the layout of the apartment.
Aside from the McCanns, I'm not sure who, if anyone, had interpreters recommended by the consulate. If I remember correctly, it was a lady who worked for the consulate who assisted Gerry with the interview on 10 May (I'd need to double-check). She may not have been a professionally trained interpreter either, but the consulate presumably found her language skills adequate to deal with the situation.
Amongst those that I've heard of, I'm not aware that Gaynor was a professionally-trained interpreter, although she does seem to have some translating experience. She speaks English fluently and no doubt Portuguese as well.
Robert wasn't a professionally-trained interpreter either, but he had helped out the police in the UK with issues involved Portuguese immigrants. At least that local UK police force therefore didn't automatically call a professional service, either. The version that would have had legal value would have been the Portuguese one in any case, although although, if a case had come to court, a defence lawyer could presumably have pointed out any errors in the English.
Contrary to what I initially thought, the witnesses would not have been able to read a written translation of their statements. Logistically, there was no time, nor the resources.
I'm not aware if a printed version of the statements were translated back to the witnesses word for word, or if it was a summary. There's simply no way of knowing.
When the context and the known or likely conditions are taken into account, I don't find it all surprising that there are apparent discrepancies between the initial statements and the ones taken a week later.
I'm aware that some people are convinced otherwise, but they tend to forget that these statements were not verbatim, there were communication issues and they weren't able to calmly read back a written translated statement. Just look at the written statement of Russel's rog (when the recorder didn't work). Someone was obviously taking notes so as to being able to provide a written record, but he was able to go through it line-by-line in order to clarify misunderstandings - and there weren't even any translation issues.
