RE: Bow mouted quiver.....
I'm assuming you have a two piecestrap on quiver or slide on like a great northern, thunderhorn, etc....
I've had the same problems as you with the arrows slipping out while shooting. They do this b/c the two individual pieces are sliding down as your bow vibrates with each shot. I take some black electrical tape and wrap it around behind each piece, enough to keep it from moving any further down the limbs...