Sinope TH1124ZB Clock/Time sync

I’ve got a Sinope TH1124ZB connected up and running beautifully for a while now - except for the clock. I can set the clock just fine writing the time to:

zigbee2mqtt/FriendlyName/set/thermostat_time

and the clock on thermostat updates and shows the correct time - and even maintains it - for a while.

The “for a while” part is the problem. After a random period, it seems to forget the time. I tried (via NodeRED) having the time get updated 1/day - but this doesn’t actually resolve the issue. Even though I set the time every day at 3am, randomly at some point the next day the time can be blank on the device (not every day, it can go weeks where it works perfectly).

So - is there something I’m missing here? Is the thermostat asking for a time-refresh but z2m doesn’t know how to repond? I can see in toZigbee.js that there is a “sinope_thermostat_time” that looks like it should be handling this, but I don’t fully understand how all these pieces fit together.