Bug, collision ? i don’t know. When a montana knockouts you, he can bug everyone on his head, just as the later Rath bug. That’s not a mechanic at all, it’s a knockout, not a knockout + hold
It’s not really a bug per se as far as I know, it’s just how unit collision in this game works; if you’re on top of another player, you bounce off. That being said, due to the numerous complaints about its use during Rath’s ult would make me very surprised if GBX doesn’t decide to change that.