I have a feeling it is related to when the player collides with the landscape. A few times I have had the bots crash into me mid-air and there has been no issues. However, if I collide with the ground, the camera will bug, and I cannot use another vehicle for the remainder of the round. Seeing this, I tested this with Lis' TGM as well. Fired a shot straight up and then turned it straight down into the ground. First shot bugged. For some reason, the game doesn't reset the camera when you collide with the ground, it seems like the game thinks the vehicle/TGM is still active after crashing into the ground. It can happen when colliding with buildings too, but not as frequently as when colliding with the terrain.