Thermostat keeps disconnection from zigbee2mqtt and doesn't show up in the device list

So, I have a Tuya thermostat connected via Zigbee. It was working flawlessly for the past three months or so. However, now it keeps disconnecting after about 2 hours and doesn’t reconnect at all. I encountered this same behavior before, but at some point, it stopped disconnecting and just worked for 3 months, and I don’t know why. Now it’s happening again, and the only way to reconnect it is by removing and reinserting the batteries, which makes it connect immediately (but only for a limited time).

Also, in my Zigbee2MQTT device list, it doesn’t show up after it disconnects. It’s not displayed as “Offline,” as I would expect, it’s simply not there at all.

I’m not very experienced, so I’d be really grateful for any help or advice. Thanks in advance!