Do you provision your Mesh APs on the wire, before moving them to where you want them?
How far are your Mesh APs from your Root/next hop APs? You can see AP neighbors in a
ZD debug (with Tech Support's help), and APs need at least 25+ RSSI from both sides for
Mesh links to form/stay connected. Is there a lot of interference in 5GHz in your environment?
Are you letting the APs choose their own channels?