I'll ask what wolf was talking about next time I see him. They were new bolts during the rebolting which saw it go fully sport from mixed gear. I'm guessing that was between 10-15 years ago , and potentially 12mm's as that's all we had back then. Saying that it isn't exactly a trade route so the expansion bolts are unlikely to have wriggled out (a problem on slate as its soft and hang dogs basically grind a bigger hole). Therefore it may be rockfall damage (loads of movement in Vivian lately). May need a new hanger or squirt of resin to secure, however it's probably still safer than the original set up (small friend and some smallish wires)