I have two GE Zwave thermostats which are practically Line of sight to the SImonXT. The third is downstairs, but within 8-10 feet of a happily working lamp-appliance plugin device.
That one thermostat goes into a malfunction state in the Alarm.com devices menu a LOT. Occasionally, when I flip to the Thermostats tab, it will show up as having been last updated about 6-7 hours previously. The update is after the malfunction happened. Also, the update time will occasionally update if I am mucking with it, but the update time is still 6-8 hours in the past.
(So I am working with it at 11:00PM, but the Last Updated entry for that thermostat has been showing up as 1:30, 1:47, and 1:51 PM variously. )
This makes absolutely no sense, unless the thermostat is seriously flaky, and the reported time comes from the device itself rather than alarm.com.