Our model 00504 outdoor temperature reading went to -25 several days ago, although it was only about 0 to -2 (Celsius) in reality. The battery low warning was there for some time, so that's the first thing we tried to correct today. Replaced the batteries, and then the reading was -18. Then we tried calibrating the outdoor temperature, but it would not go higher than -13 (it is +4 outside). (It will also step down to -23, but no lower). Why can't we get the temperature to calibrate correctly?