I'm going to use this format, to make things a bit more easy.
Date/Time: 6.4.2011/22.20 CET
Description: When I call for backup in a shotout or something, the backup arrives. But when I turn around, away from the cops and look back, they disappear (de-spawn). I don't know what to do, but my guess is, that the game puts them away or it's the mod. Sometimes it lets me have like 2 cops, but they get killed most of the time by an RPG, wich leaves you alone. (I am playing in hardcore mod).
Problem: Bots disappear when on foot.
How to recreate it: Call for backup in a shotout or something, wait for the cops to exit the vehicle, look somewhere else and look back. They will be gone.