A key safety component, the upper Z-axis auto-stop bar, was removed or otherwise came off the machine. I found the main piece nearby, but several other parts are missing. If anyone knows what happened and where those other pieces are, please let me know. (One of the missing components is non-trivial and would have to be machined.)
Until this can be restored, the machine is red-tagged. Most work done on the machine is performed at the top of the Z range; it would be far too risky to work without the auto-stop in place.