Strange behaviour of devices at a special place

acteck shared this problem 15 days ago

I have one Spirit thermostat which allways goes offline. I changed the device, but also the new device shows same problem. Same with a danfoss thermostat. Around this device are other zwave devices which work fine. Distance to controller is not more than 7-8 m. What kind of devices do interfere with zwave. I have a HUE Bridge about 1 away. But Zigbee is another frequency.

Does someone of you have a good idea, which interference this should be?