[GAMEPLAY] Ziggs Ult Will Not Activate In Some Cases

I have been unable to replicate this bug. I can describe the circumstance when it has occurred to me. (Note that I am using Quick Cast w/ range indicators)

1: Activate Ziggs ult, just before dying. (Die before the ult actually lands) 2: When the ult comes off CD, pressing R will display the range indicator but will not actually activate the skill. This effect persists until the end of the game (as far as I've been able to tell)

Edit: Might be relevant but I think both times this has happened to me, I've been displaced while the ult is casting (by a Vayne shot and by a Lee Sin kick)

This has happened to me twice in recent games, but I have not been able to manually reproduce it.