The mortal enemy to the assassin order, a Haystack out of which one cannot get out. The one weakness they never saw coming, would be their doom.
To exploit this weakness in the game, complete the quest "Childhood Sweetheart" and then fast travel to Colchestre. There, from atop the spawn location, simply jump into the Haystack. You shall see, that is the last thing you'll do. I sure hope the TemplarOrder does not get a hold of this..

When fighting Leofrith in Reptop, if you lock onto him and draw your bow, Eivor behaves in a weird way

In the mission Orphan's of the Fen, in the Area where you save Galinn from some wolves, there is a chest inside a little house. The only way to get the chest is by manually moving some stones out of the way (carry them) and crouching into the house thru a small opening.
if you open the chest, the game autosaves. Once you exit the house and move around the island, within 30 seconds you can get attacked by wolves. If that happens and you die (likely), then you are respawned back inside the little house, but this time the stones aren't moved out, so that you cannot exit the house. The stones cannot be moved from the inside.
Check screenshot.

PS. I had to rescale my screenshot to a weird resolution because the designer of this Forum must not work at Ubisoft I suppose? Any screenshot you take from a Ubisoft game is too large to be uploaded to the ubisoft forum? please demote whoever designed this feature.