Game Breaking Bugged??

Alright, this is not for me, however, I have a friend of mine, who is experiencing a literal game breaking bug. He says that at random, sometimes the game screws up to the point where it is unplayable. He explains that when he plays a normal game without issues, his ping is always a steady 30-40 ping with no dips or increases. He instantly knows when the problem occurs when he starts a game and he has 80-90 ping. The game starts off fine for about the first two minutes, then, as the game progresses, the game starts to lag an extreme amount, as if he has 500 ping, and then continues to climb. Even further into the game, at around 5 minutes, the game becomes absolutely unplayable he states. He can see players kind of moving around , he says, but they appear to glide around and don't exactly move normally. Players move at an inconsistent rate and have no animations at all. Minions will fight other minions but they will continue to fight in the same spot and will never die, but after several minutes, the minions will die, without any animation just simply disappearing and the game appears to speed up and then minions are then frozen again, infinitely attacking. He is unable to use any abilities whatsoever, and his only choice is to afk, because he can still die since he literally has no clue where the enemies are and can't see the "true" game as its happening. As for me, when I watch him play, he can still move around the map normally its simply delayed from when he clicks. He will say something like "I'm walking into the bush" And i will see him move about a second after he says he's moving. I will inform him there's an enemy there, he dies, but he doesn't see anyone attacking him or anything, he just simply dies. And then about a minute later he will see the person in the bush as if they were attacking him.

He's already re-installed the game twice, tried restarting the router mid-game, restarting his computer mid-game, he just doesn't know what's causing it, but the bug is so bad he literally cannot even play. Any suggestions on how to help him out would be great! Thanks again. (I can't believe I screwed up the title, lmao.)