So i was testing this spray desync thing and figured out that it happens 100% of the times if you start spraying, stop, tap really fast and start spraying again. It looks like your spray gets inverted
Video:
Damn, nice find. This might be enough info for Riot to be able to pinpoint the underlying cause.
This is a great video. We're looking into it!
Thanks again to all you wonderful people out there reporting bugs with videos- it makes reporting and fixing these much smoother.