Dropouts in extreme cold

The device has the last year well does its job.
The temperatures were measured fairly accurately, the radio range is sufficient for my installation, the transmitter and receiver is still running with the first batteries.

In the currently fierce temperatures below zero, the device seems to show his first weaknesses. If, for example, minus 17 degrees, the display jumps to minus 11 degrees, is a few hours at this level and then again shows the correct temp. (Now -19 degrees). New Energizer Lithium batteries can not solve your problem.
The next day, I put a brand-new unit of the same, which I really wanted to give, and to have the same problems as with the primary FR. Even at minus 15 degrees, the display jumps to minus 9 degrees. Seemingly always be the jumps 6 degrees Celsius.

Since the same error in two identical devices occurs, I go from a design flaw, or material mistake of!