Hygroscopy very inaccurate, inadequate support TFA

The positives first:
- The price is good for the functional
- The possibility of multiple channels to connect to the device is great too
- The start-up was easier than expected
- To draw the measured data on the computer works fine
- The German manual is ok

the negatives:
My main use case is to determine the humidity, and this is where the device has big problems. Unfortunately, the measured values ​​differ in some cases up to 8% from reality (compare I have several hours with two other hygrometers from two different manufacturers). Then I sat down with the support of TFA in conjunction. I was told that the values ​​can differ up to 6% in extreme cases. Unfortunately I do not know after repeated inquiry, what is the cause of this behavior.

I am considering currently know if I simply give the device back.

Who wants to only determine the temperature with the device, so that will certainly happy.