It has nothing to do with cpu or ram usage, it's just a glitch in the game. There are no more people or cars than in any other mission.
The way I got around the glitch, though, is by first walking into the trigger area (the blue circle of light thing), instead of driving into it. Then, as he jogs around the area ignoring user input, he will get close enough to the tank for the "door" on-screen button to appear, which you can press to break his jogging cycle.
He'll run over to the tank, try to get in, but it's locked, and you can then help the one-armed man kill the Columbian Cartel attackers.
Hope this helps others! Sure was a hassle for me lol.
Edit: I'm playing this on a Droid Bionic, btw, not the xperia