I would think the first step would be to strip the valve down and inspect the ball to seat sealing area. You can check this with engineers blur to ensure there is no deformation in the seat.
I'm not sure that a specification is required. For testing I would always check to see if the test equipment is x1.5 the pressure. In your case the equipment is rated to 1500 PSI. For safety purposes you could fit a PSV so that you never max out the hose / equipment.
Open to comment!