Garens Ult

recently i have played several games where garens ult did 0 damage to a player when they were near death. And i mean 0 damage. in a game i just played, on 4 separate times, against Singed, he was at around 400 hp and i ulted with Garen and it did not do any damage to him. This has happened quite frequently. Not sure if other players have reported it, but it is happening almost every game for me with Garen.

Thanks!