It's happened to me a couple times. All I really know is it seems to happen when you quickly input multiple abilities. This time it seems like it has something to with the fact I'm in the air coming out of rek'sai ult. It still does the damage every time I've had it happen but not the heal which is the strange part.
F4keS4lt1 votesIt may be possible it's something to do with rek'sai R, since Rek'sai herself can't auto attack for a second if she presses Q mid air. Has it happened with other ults or just when you "smash your keyboard"
Gloppa1 votesI can't remember if other ults caused it, but I do know that it's happened without rek'sai ult being a part of it. I know there was another thread with his own e stopping the heal part.
F4keS4lt1 votesI may have possibly experienced it myself. Can't recall correctly. Been a while since I played Sylas.
I do know that there is a small lockout during his E, so maybe it doesn't register that you used W since it may not be expecting it. I'm no programmer or an expert.
DiscWizard11 votesI noticed this too, it was not healing, ptrry sure its 9.10