Revenant Unrelenting Assault disjoint bug
I figured part of when the bug occurs more precisely. When you would go up a ledge or go to a posture you would fall down from. The Revenant stops the assault and stands still onto a stable footing nearby, thus losing the ability.
It could be fixed by making the revenant finish the attack regardless of personal position even if it makes them airborne or go inside ground and teleport them next to the nearest stable footing next to their target as the attack finishes.