Howdy friends!
Just some passing wisdom from a person who’s (now) pulled their hair out fighting zigbee issues -
I had a working Openhab setup (including zigbee) and decided to make everything neat and tidy and wrapped it all up in a nice metal box (a rack with a closing door) - mostly so my partner would stop nagging me about cables everywhere. 
I booted Openhab back up and lo and behold everything except my zigbee switches/lights were working on. I went on a several day adventure tailing detailed debug logs, double checking changes, and literally about to pull up the source code for the zigbee binding itself to understand what was going on.
In a fit of rage, I pulled it back of the nice rack - booted up again, and everything was fine - zigbee was happy as could be.
PSA: closed metal racks actually make radios behave differently. What I thought was some insane software bug turned out to be little more than me wrapping it in a faraday cage - and getting almost no reception to my closest mains powered zigbee device. 