calling for backup

backdrop, check. strobes and triggers, check. backup speedlites, check.  backup batteries and cards, check. this once-per-year company session includes dancers scheduled 5+ per hour for 4 hours, check. 1/3 through our studio session the shutter sync is wrong. half of my frames are showing up black. usually this means the sync is set too high for the studio strobes, but at 1/160 and slower still at 1/125, that should not be the case. the viewfinder goes entirely black. i am now shooting blind and beginning to sweat. i pull off the lens and to my horror, the mirror literally falls onto the floor. my heart surely stops, and at very least, skips a beat. reinsert the mirror. (it should *never* fall out. in 30 years, i've never seen anything like this.) reattach the lens. fire. we have a shot, and it is synching properly. but it's out of  focus and i cannot use the viewfinder in order to focus the lens. someone finds us a fabric tape measure. we take to the floor, marking out 5' intervals between the camera lens and the dancer. finding our total length, i return to the camera and set the lens manually to the correct distance. fire. check. we're back in business, but for the rest of the day i have no visibility through the viewfinder. here are some of our results from our indoor jazz company session.  one parent asked, "do you have a backup camera?" well, i didn't. i do now...