I have a Circon UHC-300 Controller at a medical office that regularly loses its application and configuration.

I always happens near 8:30 PM, but not always on the same night. It happens once or twice per week. I have visited the site near the time when this happens, but never witnessed it actually happen.

I have replaced the controller, eliminating that option. I also added a UPS between the 120 and control transformer. There are no other controllers on the system, just this one. There is a VFD drive tied to the controller via LON, and a LON remote space sensor, both of these devices work just fine.

I am trying to find a way to identify what could be causing the controller to lose the configuration.

Any suggestions?