As Frans van Liere succinctly puts it in An Introduction to the Medieval Bible (Cambridge 2014),

Contrary to popular perception, there was no blanket prohibition against biblical translation in the vernacular in the middle ages. (p 203)

I've written on this subject a bit before, the relevant part here:

Why was translating the bible considered heretical in the middle ages?

It wasn't. For the most part translation of bibles into vernacular - whether French, German, Dutch, English, etc - was carried on without comment from ecclesiastics during the middle ages. When it did become an issue we find that it is results from accusations of heresy (or heretical interpretation contained therein), and not production as a heresy in and of itself. So, prohibitions on vernacular bibles in Toulouse and other places in southern France during the 13th century were related to stamping out heresy there; likewise, the German Emperor of the 14th century Charles IV in his famous outlawing of vernacular literature was aimed at heretical sermonizing and pamphletizing; and again, edicts against literature of the Beguines in the Lowlands and the Lollards in England in the late middle ages had to do with the content of preaching and not being in vernacular per se. In fact in 1199 Pope Innocent III instructed (although it was not always followed) the following to priests and bishops when there is suspicion of 'troubling behaviour' due to heretical beliefs incorporated in vernacular writings:

Inquire and find out the truth: who was the translator of that translation, what was the intention of the translator, what do its users believe, why do they teach, and do they uphold the apostolic see and the catholic faith?

Answering further, we should also dispose of the idea that the bible was always presented and used as one book, or even in a form close to what we would recognize today. Most experiences of the bible, in particular in the vernacular, were fragmentary or paraphrased, whether latin or vernacular. They could even have been rewritten in prose or poetry. 'Christianity' and 'the Bible' were not static objects of worship as they are now, they were the basis of culture, the stories people grew up with hearing and telling. Mileage may vary on the accuracy of the stories told, or of how much they mix with other parts of culture.