Alt+4 isn't upgrading Vyper ult

[tankorsmash]

This has happened several times, often once per match. Seems like maybe it's many ults work like this, but definitely Vyper. Usually Alt+1,2,3 all upgrades my abilities no problem. I've reset my ability keybinds to default and it still happens.

Matchid: 45121629 at about 20 minutes in, I cast my ult looking at the ground/nothing