(Added:) Please delete this post if it does not meet the required standard of the subreddit.

No absolutely 'accurate' documentary either about the Vikings or about any other topic in the Middle Ages can be created, but as for the former [Vikings], I suppose we can regard following ones produced mainly in the latest decade as relatively 'good' in light of the recent academic standard:

• Njál's Saga (trailer in Youtube: you can also find the link to DVD online shop there in the commentary section) (with English subtitle): films one or two episodes from Njál's saga, one of the most famous saga of the Icelanders, alleged set around 1000 CE Iceland. The comments of several researchers of different fields of study (historians and literature researchers as well) on how to interpret this saga and the filmed episode(s) are also attached in the DVD.
• Short film series released from Ribe Viking Centers (also on Youtube (on their channel)): Especially RIPA Documentary (Short introductory films on the craftwork in the Viking Age), Vikings by the Wadden Sea, and RIPA (fictional historical drama series) seem to be relatively fine. How to enable their English subtitle on Youtube can be varied (so that you can be sure to enable them), though.
• (Added:) Some national museums in Europe where the Vikings left for or invaded have also published relatively good academic quality of 'documentaries', i.e. the the online exhibition of relevant artifacts with the annotations by specialists. I'd especially recommend Viking Ireland series among them.