DIAGNOSIS This is usually caused by a brief power interruption that triggers a reboot. Without a properly functioning C-wire, the thermostat relies on its internal memory, which can get corrupted during a brownout or quick power cycle.
FIX Confirm your C-wire is providing constant power. Follow the steps for checking the C-wire connection at the thermostat and furnace from the 'blank screen' fix above. A solid C-wire connection is the single biggest factor in schedule and setting stability. Once verified, go to the thermostat and manually re-enter your schedule. Then, perform a manual reboot: pull the display off the wall plate, wait 15 seconds, and snap it back on. See if the schedule sticks after this clean boot.
IF THAT DIDN'T WORK There's a system reset that clears all settings and restores factory defaults. Go to Menu > Preferences > Restore Factory Defaults. You'll have to set up Wi-Fi and your schedule again from scratch, but this can clear out corrupted memory that's causing the reset loop. It's a pain, but it often works.
HEADS UP If you're making schedule changes in the Total Connect Comfort app, ensure you tap 'Save' or 'Done' and wait for the confirmation. Also, know that if someone changes the schedule directly on the thermostat while you're looking at the app, it can cause a sync conflict that appears like a reset. Pick one place to manage the schedule.