The first step I would try is a power cycle of the thermostat. Pull it off the wall, remove batteries, wait about 2 minutes, put batteries back and plug it back on the mounting plate. Edit and resave schedules in Alarm.com. Does the problem continue?
If so, I would recommend deleting that affected thermostat from the panel, wait 5 minutes, then relearn the thermostat.
Reconfigure the schedule for the new thermostat in the app. Does this resolve the problem syncing?