Gateway, THUM - Abnormal temperature

I'm testing a set of new devices in a air conditioned room (about 25 Celsius degree). The devices consist of Gateway, Daisy chain starter, and two Daisy THUM that I recently purchased.
Yesterday, sensors measured normal room temperature correctly. Today, they measure abnormal temperatures 28 to 30 Celsius degree. I didn't calibrate the sensors. I didn't change any settings of calibration.
I tried to to fix the problem by resetting the Gateway according to Sensors Platform User Manual Section 7. However, the problem was not fixed.
What could cause the problem? How can I let the sensors to return the factory calibration?

Are you sure that the sensors are off and not your AC unit? It is extremely odd that 2 sensors would be off by the same amount.

We assume that the sensors are clean and that this is not a dirty environment that they are running in.
Here is a page explaining how sensors do drift - https://infrasensing.com/lab/sensor-drifting.asp

There is no factory calibration. There is an option to perform an offset on temperature but based on what you posted this was not set.

You can always request a RMA within your 1 year warranty. The units will then be inspected and tested.

Thanks for your prompt feedback. Today I did the test again with the following procedure:

1. In my working room which is clean and air conditioned, I connected a Gateway, a Daisy Starter, two Daisy THUM. I hung Daisy THUM on a wall to prevent heat being accumulated on sensors. (See attached photos)
2. I measured the initial temperature at 9:29AM.
Int. Temp1 = 29.67
Daisy Sensor1 = 27.31
Daisy Sensor3 = 26.24
3. Let the test system work.
4. I measured again at 14:41PM.
Int. Temp1 = 33.13
Daisy Sensor1 = 30.56
Daisy Sensor3 = 28.6

We can find the following problems.
Problem 1. The initial value of Int. Temp1 is abnormally high.
Problem 2. The initial values of Daisy Sensor1 and 3 have big deviation of precision.
Problem 3. The accuracy deviates significantly while sensors work.

Please help fix the problems.

https://drive.google.com/file/d/1gEHSHc5o67JDngDcNk_28H3zRoBdnhuT/view?usp=share_link

It seems that there is a heat source probably which causes the rise. As all of them are rising up.
Can you further check it all throughout the day?

After long running, the sensors are stabilized. Thanks for your support.