Not sure if this hasn't been discussed before, but it was probably a problem with the 810 beta and has long since been fixed...
I am running Dianemo S, in case that's relevant.
Problem: my zwave stick has the full config downloaded from a Merten controller. Haven't had any problems ever, doing this. But now, a whole bunch of lights disappear after I reload the router. Then, after some time (an hour? maybe less), they come back and the system asks me te reload the router so I can use them. Unfortunately, when I reload the router, they disappear again.