I've also had this happen, I'm not sure if it's an interaction which they will keep but I don't think it qualifies as a bug. Once it's channeled you have to stun Mo&Krill to cancel the ult so Doorman teleporting you to the hotel shouldn't cancel the ult.
It's a super annoying combo to be the victim of but at the same time I'm not sure if your opponents should be additionally punished for stacking single target ults on one person since you are avoiding the damage you'd take while Mo&Krill are holding you in place on the map if Doorman also ults you.