Can't help you on that one, I'll give it a go myself and see if I have better luck. I do remember a pilot of a different platform saying that this method of coordinate-based bombing isn't exactly loved in real applications because unless you have someone giving you an exact target position to the last metre, the bombs won't be accurate, and the fact that it uses two systems that are prone to errors (CCRP and INS) makes it impractical unless you're saturating a large area or target.
EDIT: Tried it in the Mirage 2000, I think I cracked it. The INS we use is accurate to a pretty decent extent, and it accepts decimal inputs for for distance and heading. However, our blessed little Mission Editor doesn't do decimals for degrees and the INS only takes two decimals for distance! I flew four attacks, two with Mk 82 and two with Snakeyes. In all of them, the target according to the INS was within 1000ft to either side of the intended target, but that's way too far for small bombs to still have an effect. Not sure if there's a way to get the decimals out of the heading properly. Has anyone tried it with coordinates instead of rho/theta?