Unresponsive right click

Had a couple of games where halfway through right click becomes hugely unresponsive, only registering about 1 in 5 times. It's not a problem with my mouse because it works perfectly fine out of league. It's not a problem with lag because everything else like smartcast skills are good. It's not even a problem with the move command because I can bind it to another key and it works.

Apparently this was a problem about two years ago without any clear resolution in various threads I've found. Does anyone know what's causing it?