On-release bugs

Every time something new is released, there seems to be some sort of game-breaking bug that forces Riot to disable a champion or an item. Every time a bug is discovered, it takes forever for Riot to figure out how to replicate it, and then another couple centuries to figure out how to fix it. Remember when Viktor was disabled for most of an LCS split and Caitlyn's auto-attacks were bugged for almost the half the season? Every time I see the "X has been disabled because of an in-game bug", that's all I get. I have to do some detective work in order to find out what the bug even was.

This tells me that Riot doesn't playtest very much, and that they a) have a bad workflow regarding bugs, and b) don't want to admit what their bugs are.