Arbitration (Defense) - failure due to host migration.

[Grizeus]

When the host dies or disconnects, the map is 're-loaded' and all current buffs are removed from players, while enemies remain just as they were.

That process is not particular to defense, but in defense arbitrations, it can cause the mission to instantly fail if it happens in the middle of a wave; I've recently seen a case where after the host migrates, the game loads back up and the defense target dies immediately, resulting in mission failure.

I'm not sure if it would be possible to avoid or 'fix' that in any way, but I thought it was worth a mention, as it doesn't seem exactly intended.