Rheem RGPR-10E-BRM a/c sometimes doesn't respond when manually lowering temperature. The system behaves normally until bedtime, when it's our habit to manually lower the temperature considerably (e.g. from 75F to 69F) just before popping into bed.

At that time we lower the temperature and set the fan to 'on' because we prefer constant air movement at night. The thermostat makes all the normal-sounding clicking noises, but neither the fan nor the compressor start. Unplugging the furnace unit for just a moment restores normal operation. Nothing I have thought of doing with the thermostat (including selecting 'off' or removing it from the base helps.

It may be related to the fact that my wife selects the fan to ON and then lowers the temperature. I use the opposite order. I think that I don't have the problem but she does, but I could be mis-remembering the history.