Zigbee aqara sensors go to "unavailable"

I have a bunch of aqara door sensors, and they keep going to “unavailable” state. One of them just did it about 4 hours after pairing. Then triggering the open/closed signal doesn’t revive the device, have to go into pairing.

A, trying to figure out what even makes them “unavailable”, since they’re battery sensors and should just be considered asleep until they send something… or does zigbee have a periodic signal?
B, what other solutions are out there? Is zigbee2mqtt any better? Any way to wake it up without going through pairing?

HUSBZB-1 stick. Working flawlessly with 20 zwave devices. But zigbee has been a pain. Stick is extended away from the PC.
Zigbee now set to channel 20 away from my wifi on channel 1.
Only these 5 aqara sensors, no repeaters.
I assume the range is fine because it has never missed an open/closed signal when working. And one garage door is still working for weeks while the other is unavailable a few times, sensors literally 6" from each other.

Cheers friends!