Strange indeed. I cannot imagine Radar Contact or Active Sky interfering with Pushback.
Never heard of DBS, though.
As far as AES is concerned, I use it with FS2Crew all the time with no problem whatsoever.
If FS2Crew Ground Crew says "Please release brakes" and you respond "Brakes released" you should definitely get a response by the Ground Crew. Otherwise, try saying "Brake released" without the s. I noticed that words ending with an "s" get confused by the speech recognition system at times. E.g. when I pass Transition Altitude and I have to speak the altimeter setting, I always do without the "s", speaking "Altimeter one zero one three" instead of "Altimeters". Works great :-)