Smart-cast with ranged indicators is extremely buggy

I've been playing like this since 2012, and haven't had a problem since a few patches ago when Riot added the "cast 1st spell upon pressing 2nd spell key" as a feature. It is most apparent when you are CC'd, but it's more than just that. Simply trying to do combos fast will leave you with the wrong cursor for your spells (e.g. LeBlanc will have her W indicator trying to cast Q or E, Ryze can be left with his E indicator trying to Q, Viktor's W and E can get messed up, etc...)

I know this only impacts ~10% of players (as a generous estimate) but for those it does, it is very annoying and is a significant impact in games. I'm trying to figure out how to reproduce it 100%, if anyone has figured it out please let Riot know! Thanks :D