Recently I have been encountering fatal crashes when the game updates a quest/raid objective or upon completing a marked/main quest (All within 5-15 minutes of loading my save game).
I have aprox 37 hours played since launch, but these crashes have only started as of today. All of my drivers are up to date and I have verified the game files to no avail.

I feel these crashes coincide with the game's auto-save feature during quests. However, I have had other successful auto-saves happen from things such as synchronization points.
Another cause I believe, could be from communication loss/error with the ubisoft servers although there is no pop-up to say that the connection is lost.

I doubt it has anything to do with ubisoft+ sevice itself, but the loss of server conection or overloaded servers are more likely culprits.
I have about 37 hours played since release and close to 50% main story complete. However, the game has started CTD for me today every time I tried to raid the Tonbridge Monasteries in Cent or go near the main fort in Cent, all encounters happening within 10 - 15 minutes of loading my save. I am leaning more to it crashing during information updates to the serve, such as when completing/updating quest objectives or raid objectives. The only crashes I have had prior were mostly during cutscenes and only minimised the game or changed it from fullscreen to borderless window. I did have the lost connection to server notifictaion pop up a couple of times yesterday, but it never effecting the gameplay and disappeared pretty soon after.
All my drivers are also up to date, my files are fine and my PC should definitly handle it.

From what I have seen, this game is definitely not polished. There are still a few bugs, glitches and inconsistencies around the game, a couple that stand out good is the flying kayak in near one of the settlements in Vinland or the floating fences in the fields just north of Lunden.