NS panel show 655deg C when the temperatur drops below low

Iam using several Temp sensors via the NS Panel pro Zigbee gateway. When the ambient temperatur of the sensors drops below Zero degrees the NS Panel shows 655 degrees.
Also the graph became useless because its a continious line at 655 degrees,. above freezing point the graph is jumping to Zero degrees.

This issue is being investigated, I will let you know when a result is reached.