[gameplay] killing zyra or kogmaw with ult as darius will sometimes put it on cooldown

as darius if you ult kogmaw or zyra sometimes the ult will go on cooldown without letting you use it again for a few seconds. it does not happen every time but i tested it in a bot game and it does happen every now and then. the buff icon will still show saying you can use it again but the ability is on cooldown and you cant use it steps to reproduce

1. ult a low health zyra or kogmaw as darius

happens about 4/10 times id say? idk