Setup and transmit errors

I have a Vera2 with 8 devices in my summerhouse. All devices within 12-15 meters straight-line, and on 3 floors (with Vera2 in the middle). I have had the system set up 3 times with success but after some time some of the devices are unreachable and there is simple no logic for which ones fail. Of corse when I’m 600km I’m away and want to turn on central heating…
I have used default parameters when devices configured. All devices paired with Vera2 with bringing the devices to Vera2 (not the opposite way walking around).
I think I have a transmission quality issue but not sure. Don’t understand why some devices available and others not, even within 1 meter. Shouldn’t zwave broadcasting ensure connectivity. And remember after setup all devices seems to work fine for a while.

I repaired the network and now working again…not sure for how long.