RPG FIRE and DEFECTIVE NADES

If I fire my rpg directly on target nothing happens! I always have to shoot ground or a wall near the target to be effective. Thats odd. Sometime my nades don t explode and thats a big problem when there more than one enemies after me. Any clues?

Well..the rpg...idk that should happen...the nades sometimes sink into the ground and sometimes explode, and sometimes dont, if you are lagging badly, then yeah, it will seem like the nade never exploded.