Yeah, that shooting at nothing happened to me yesterday. I should of added "Hardcore Tweaker" to my post. A lot of the time I'll get rid of my Allies, they just get in my way and I like to fight by myself. Probably can't do it on the mission your talking about, sounds like a "trigger". The path finding does give some WTF moments. MoWCH is a tough game and the way I play it that really works for me(even with the bugs).
Played the first bonus mission yesterday(Hard) and I gave myself more setup time. That mission alone should give me hours and hours of replay value.
http://youtu.be/iu6XTX8unZA