Weird Lissandra Ultimate Bug

Hello everyone!

So I recently played a normal game with a friend when I came across this bug. If the video is confusing, here's the jist of it, our team was sieging the enemies tier 2 mid turret and we were doing fairly well. That's when Lissandra ulted and everyone on our team froze. My game completely froze, I asked my friend over voice comms and he said his game froze aswell. Multiple times I tried to alt-tab, but it didn't work, so I resorted to forcefully shutting down my computer. When I finally came back into the game, the enemy team was at our Nexus, which tells me that their games didn't freeze. They won the game off this. At the time, I thought it had something to do with the servers, but after watching the replay a few times and seeing that everyone on our team disconnect at different times (which implies that they had to quit League aswell) I knew that it had something to do with her ultimate. I don't if you can call this a game-breaking bug, but it really needs a hot-fix.