ARB bolt failures

Preparing for a week in Moab, I removed my differential covers for inspection. On my front D 30, 3 of the 6 small cap screws had broken off just under the heads and the heads and the threaded portion were laying in a cavity in the bottom of the pumpkin. I cannot imagine how the threaded remainder of the cap screws backed out without damaging the copper air line. I am in the process of trying to get a new set of fastenings as I would like to replace all of them. I cannot see a way to tighten the screws without removing the collar which holds the sliding portion of the locker. The gear set appears to be undamaged. The rear assembly (D-44) was intact. Has anyone had a similar experience with ARB's? The units are approx 3 yr old and are in a 00 TJ which is used on moderate difficulty trails.