Galio Ultimate Bug

ARAM match, using Galio. Twice I managed to ult only to have him hover in mid air (2 seconds) and then then glitch to the floor, with no impact and CD timer start. Definitely managed to select a allied champion and he did partially jump up. May have something to do with Fiddlesticks Q or some other CC?

If this isn't a bug, can someone tell me explicitly when Galio becomes invulnerable during his ult. Will help out greatly!

Thanks.

EDIT: Looked at the replay, both times show me stationary on the floor even after casting, although during Gameplay i was midair. First time got hit by an indirect Fiddle E (last bounce), the second a Wukong ult from bush.