Seems like there is a bug with Doomfist’s ultimate on Chateau when using it in the small room in the dungeon(the one with the small health pack).
I’ve had it couple of times, first time I though there was some glitch that I entered the ult mode without any HP left, but this time I was able to record it. As you can see, I have quite enough HP and dropping down just instantly killed me.
VIdeo: Doomfist WTF??? - YouTube