Yo I think this is a feature not a bug. This should happen for enemies that are marked or something.
They need to explain in-game as I googled the weapon to learn more about it and how it should be used and found could not find a wiki or official source.
@LordXOne I think your hypothesis is correct. I suspected homing due to how they moved towards my target not thinking that I was also moving the cursor there, but looking at the videos you provided I can see that's clearly not the case and the grenades avoid the target. Quite a frustrating bug for such an otherwise dependable gunner option.
I now suspect it is not specifically related to the movement of the vehicle but of the vehicle turret part, the gun that the driver controls. I have seen the 40mm Grenade Launcher redirect when that part moves. The MAV does not have a movable turret for the driver and I don't think I have seen this on the MAV, have you?
