Mental break: Manhunter...

...or the new way to get killed from the inside?

I'm playing in a mountain base, and in order to counter the higher probality of infestation in A17, I have 15+ bears who follow my brawler. Already fought two infestations, and that worked very well. I also use them to attack tribal raids when I am bored to see them being destroyed in my killbox.

However, I just had half my colony killed when 5 of my bears decided to go on a mental break: Manhunter.

I had no idea that was possible. Any way to avoid that?