I have a dual system in my home with Honeywell T8195B thermostats. I probably haven't used my front system in 20 years, and the rear one I use very rarely. When I turned on my heat last night, I noticed the time on the timer was incorrect. I turned the adjusting knob and nothing moved. I did this on the front thermostat and had the same results. The voltage between the C & R terminals is 27.6 vac. I can hear the timer clock click, and the dial does turn on its own, but I can't manually adjust it. Do you have any suggestions to address this issue?