[GAMEPLAY] Nexus Blitz - Event ended instantly and assigned a (random?) winner

Event countdown was normal but as soon as the event was supposed to begin it instantly began the winner animation, with party balloons and reward distributed (BF shields). As far as I could see, the type of event was not even displayed to the client.

Replay file: https://drive.google.com/open?id=1o7gXXRkV541e5zTuD-vZNxEQZgByafOi Event (fails to) occur at roughly ~12:18 on the game clock

Match link: https://matchhistory.na.leagueoflegends.com/en/#match-details/NA1/2849487545/229791595?tab=overview

No idea how to reproduce. Got ~40 matches in nexus blitz and this is the first I've seen or heard of it. I would like to note that it should be too early for the sudden death event which seems to cause so many issues, so this is unrelated.