Since Riot doesn't care here's a fun thing about ARAM towers.
Been about a year now and is more common and I'm more than sure 100% able to reproduce.
Whenever someone is being shot with a tower it stacks the damage over time, but for some reason it likes to stack the damage and keep it on the first shot on a new target, mainly champions.
So if the tower is wailing on a cannon minion with 2 shots already on it, switches focus to someone else, the 3rd shot will still do consecutive damage to that new target.
So yeah... might wanna fix this since its in just about every ARAM game now. :D