The “Route discovery failed” error means:
# An attempt to discover a route has failed due to a reason other than a
# lack of routing capacity
Which is not terribly helpful.
It does suggest, though, that your network is fine in terms of number of routers etc. You might start by looking for sources of interference. There’s a very thorough post about that here:
Which sensors are not working? If everything is working, the problem may be intermittent and the network is managing it (which is what it’s designed to do). There’s a lot to be said for “If it ain’t broke, don’t fix it…”