While climbing Southern Man on lead first G/U attempt after failed O/S I clipped below shallow roof and diverted right through the crux moves and then began to move back left. As I approached the ultimate clip I had two good crimps and pulled rope up to clip and did so fine, though tired. Finished the route with no issue though the section described was run-out. . Upon descending I heard from two spectators that while I was pulling rope out to clip the ultimate quickdraw, the one preceding it had unclipped itself. They had kept quiet so as not to worry. Had I fallen off while clipping in this position the fall would have been likely ~10m and left me at least near the first bolt. Luckily I hadn’t known and carried on regardless. They hadn’t noticed it before and didn’t know what caused it.