On the Coxwell map:
If someone joins this map at the start and then changes teams from Agatha to Mason then the game cannot be won be Mason in the final stage, even if you kill all of the Agatha players.
When it gets to the final stage where Agatha have to survive the onslaught the final player to kill is technically on Mason so the game cannot be won by Mason.
You can recreate this with the AI in the offline mode, as you always start the game as Agatha, switch to Mason and you will not be able to win the map as Mason.
I moved to Mason in an online match today and discovered this bug, I moved back to Mason when I realised what was happening after all of Agatha were dead and the game ended immediately as soon as I switched back to my original team.
I have seen Mason be unable to finish Coxwell multiple times but not known what the cause was until now.