Bug with Courage of the Colossus

Courage seems to have some inconsistencies with when it activates - I just played a game with a Vlad who took the mastery and was able to proc it. I have no idea why he was able to proc it, or when it activated for him, but during several team fights he very clearly had the shield and the green bubble animation.

As far as I know, Vlad doesn't have hard CC.

Unfortunately, I didn't record the game, so all I have is a picture of him having taken the mastery... https://i.imgflip.com/1e0v6i.jpg