Litle zigbee lumi sensors delay

I’m testing a litlle Lumi zigbee temp sensor. The little 3x3 cm sensors. In fact it works, but measurments are very random in time. So sometimes updates are frequent (around a minute) sometimes it’s completely random (more than 20 minutes). So you can’t use it for thermostatic use. It can’t be the distance. Only5 meters with one thin wall.

Anyone a idea,or a better solution? I want to stay at Zigbee, because it’s a mesh network.