Trane Thermostat TAYSTAT500 when programmed will not hold the Heat temperature from 10 p.m. to 7 a.m. at 60 degrees. Around 3:30 a.m., it goes back up to 64 degrees without it ever having been set at 64--either heat or cool. New batteries and complete attempt to reprogram thermostat several times have failed to fix the problem. Trying to save electricity and unit itself is functioning well. Help, please