I can think of a number of problems with these sorts of teleoperated military vehicles. The obvious one is that if it's radio controlled the radio signals could be jammed, either by broadcasting random signals on the relevant frequencies or by recording radio activity on the robo-band then just replaying it in an endless loop, causing the robot to endlessly repeat some harmless action. Even if the radio signals were encrypted the simple radio record and playback method would fool or confuse the droid.

The other potentially much bigger problem is what happens if one of these machines falls into the hands of terrorists and they drive it through a major city? Even in the unlikely event that terrorists could never acquire such a weapon couldn't someone just homebrew a similar radio controlled buggy and strap a gun to it?