I have same problem with RN2483. Somewhere starting at -11°C and down 'radio tx xxxx' command is not sending data out, at least receiver get nothing. I tested 4 modules and all have same issue. Firmware version is 1.0.1. When I bring it back to warm environment then it started to work again. I tested it also such a way that first I cooled it down to -20°C, then powered on and started to send data. Receiver which was in warm environment got nothing. When I brought TX back to warm and all the time it sent data but in this case receiver never get data. After reset the TX receiver started to get data normally. So far I didn't find any workaround to get TX working correctly.
Also I made test that I put both TX and RX to -20°C. Receiver stopped to receive data too at low temperatures. Then I used another TX at +25° for data transmission. RX in -20° didn't receive any data.
Sounds serious hardware issue. Time to add ticket to Microchip. Or any suggestions?