I have a sonoff dongle max for my zigbee network. It has worked great but every few days I would have a random device go offline and I would have to unplug the device and plug it back in to get it back. It was usually these cheap zigbee plugs I bought so I assumed it was them. Well a couple of weeks ago I was doing some network upgrades and decided to finally mount my sonoff dongle max instead of just sitting on a shelf. Well mounting it meant it was about an extra foot from my server rack and wifi node. I havent had a single device go offline since. So if you are getting random devices disconnecting occasionally it may just be your coordinator placement.