Up2 low temperature issues

we are using the Up2 N4200 4GB/32GB in our product. Now we recognized that some boards (~5 out of 50) have problems with low operating temperatures (0-5°C). They restart, freeze (after around 2-5 mins) or do not even boot up. The blue light is on but everything else incl. the fan is off when it doesn't boot up. We made sure that our power supply is not the reason because we saw the issues with our own extension board with power supply, as well as with a 5V/6A DC jack power supply. We have the miniPCIe LTE module connected. The CPU temperature is 8-14°C.
As soon as we bring the boards back to room temperature they work normally again. This is super annoying.

Does anybody have an idea what the reason could be and how to prevent this?