As an addition to the comments of D. Mealand & others, I wonder
if those (few) passages in the gospels where Jesus's (Aramaic)
words are transliterated & then translated into Greek (eg, Mk
5:41) might be worth consideration in this matter. There are
various different attempts to explain this phenomenon, but it
seems to me that in these cases the text is (also) "admitting"
that it is a translation -- even though that admission itself is
of course a narrative device.