We have purchased dozens of AD592CNZ temperature sesnors to be used in between 5degC to 80degC,

We are using DT800 datataker for data acquisition. Currently, there are 12 of them located at the same point in the climatic chamber and We have no problem measuring temperatures more than 20degC all sensors shows the correct value> However when it is over 20degC, each sensor shows diffrent value shuch from 20degC to 65-70 degC and sometimes it goes minus temperatures. We know for the fact that temperature is exactly 10 degC.

Why would each sensor show different values? when we use thermocouples they work just fine.