1. Go to Virtual Garage.
2. Choose M4 Scorcher and load into VR.
3. Sit on gunner position and shoot with main caliber into the ground near yourself. You will hear the sound of shot but no sound of shell explosion.
4. Change position to Commander, choose GMG and shoot near yourself. You will not hear grenades explosions.
Looks like this problem is on all vehicles. I checked Hunter GMG and Strider GMG. No sounds of grenades explosions in first person view.
Additional steps to reproduce:
1. Put two armed offroads in editor.
2. Get in gunner seat of one of them and destroy another one (you should be in first person view).
3. You will not hear an explosion.