We are running into trouble that Sarge AI (1.5.2) is being rather malicious. Survivors and and even military occasionally open fire on hero players (even if these have no murders and even if they haven't ever killed a survivor/soldier.) Looking through the logs, they even seem to be attacking themselves occasionally. Further more, although they are not supposed to search for vehicles, they tend to want to hitch a ride and then either just sit there or drive away once you get out.
I even tried setting the friendly AI side to WEST, but the first survivor patrol opened fire on me and injured me and all I got was the usual "blue on blue, cease fire" messages as I was returning fire.
