Gangplank Ult. Disappearing/Invisible

I recently played a game against a Gankgplank who's ult appeared then disappeared but still caused aoe damage. Unfortunately I do not have any footage from that game but, my teammates and I would walk around then be hit with random waves of damage at times. I'm not sure if anyone else has experienced this but it is quite a nuisance. I'm sure this was caused by the recent Gangplank update as well.