Some sonoff 01minizb randomly become unreachable

I have a network of 20 sonoff 01minizb managed with conbee2 and deconz, the problem is that sometime, let’s say every couple of days, one of the device, random becomes unreachable, and returns reachable either by itself after x hours or immediately if I paring again or immediately if via vnc I make a request for “nwk address”.
any ideas on reason?
there is an api way to make the same “nwk address” request in order to automate the recovery of the device?