Betrays on Arrival Escort Architect Mission Bug

I've noticed a bug when Escorting a Master Mind to the Exit.
In the scenario as you get there he thanks you for all your assistance then says he has to tie up the last loose end *you* The problem is that While the Mastermind will turn on you, his pets do not.
They seem to go neutral faction and will even support you against their master if the Mastermind hits them with an AoE while targeting you. The Mastermind will attempt to summon new pets, but with the old ones still around no new ones appear.
I would assume that the easiest way to fix this would be for the MM to dismiss its pets just before it turns on you.