I agree that a reboot option should be implemented, and not just in this one device, but in every device technically capable of it.
The $500+ figure is based on what their website lists for a 10-pack times 9 = 90⊠You wrote that you have 87 units, so thatâs why itâs so expensive. Maybe if you ordered 90 units, theyâd offer a better price. But Iâm guessing the price will still be too high. 
I donât know what type of business you run, but since you service 87 apartments, a $500+ investment doesnât seem that painful compared to walking around and manually operating it.
$500 divided by 87 apartments, divided by twelve months, equals monthly per apartment $0.4789272030651341 Thatâs just under $6 per apartment at one timeâŠ
Itâs a prosthetic device, but itâs either that or Sonoff should add a ârebootâ option⊠although knowing the speed of change and the general process of adding new features, Iâm afraid it will either take months/years or not happen at all.
Unless an alternative firmware exists that would have this option and could be installed.
As for ZigBee sensors disconnecting, Iâve also experienced this, and sometimes I still notice it occasionally.
Exactly the same setup as yours: the bridge and the 05P. In my case, only physically relocating the bridge helped, as the 05Ps were constantly losing signal. However, rebooting the bridge didnât help; only manually pressing the button on the 05P helped.
Check your signal levels for those 05Ps. Mine has to be no higher than 70-74, otherwise it starts disconnecting.