Self casting movement speed buffs while holding right click

What I do that leads up to the bug:

1. holding right click to move my champion.
2. Alt+spell button to self cast movement speed spell (karma E, Zilean E, Orianna W) without releasing right click
3. continue to hold down right click The Result: The champion will move to the location of the cursor at the time the spell was cast and stop moving even though right click is still being held down at another location.