As wa2crk suggested, the set screw that holds the crank handle to the shaft had come slightly loose. The crank handle had shifted slightly on the shaft, which left the gear on the back of the handle slightly out of mesh with the gear set the drives the indicator dial on the outside.
It took quite a bit of fiddling (and some swearing) to get everything all lined back up, meshing and properly seated but thanks to my new extra-long 3/32" allen wrench, a cold beer and your expert advice, I'm back up and running.
Many thanks to all. Cheers!
