Night's veil bug (gameplay)

In my Yasuo game, night's veil showed a 5 second cooldown every few seconds (three times) and i had to activate every one of the separate cooldowns in order to start the actual cooldown. If you want to reproduce this just buy nights veil on any champion activate it and have it consume a spell... kinda ruins the item if you have to manage 4 cooldowns to use the damn thing <3