[GAMEPLAY] Katarina ult won't be interrupted by Lissandra's ult

In a recent game I played in Summoner's Rift, in a 3 v 3 fight at bot lane, enemy used her ultimate spell, as a response to that from our team ulted ; but it didn't stop 's ult and she was simply able to kill everyone when 's ult ended.

There is no clear description that I could get to explain how to reproduce the issue; but what I can say, if that helps, is that they casted their ultimate spells almost at the same time.

Edit: This issue keeps happening at least once or twice per game that I play and includes Lissandra and Katarina in opposite teams.