[cjthomson]

...
software from here. Once this was done I re-flashed the RX and the Wireless Display but the problem still seems to exist.

Hi Chris

To solve this issue downgrade your AVR boards version to v1.6.21, no matter what IDE version you are using and reprogram the RX unit. AVR boards 1.6.22 or AVR board 1.6.23 are the cause of the problem.
This matter is covered on several posts on the forum, also there is also a note on the software download page:

IMPORTANT:
Always compile using the provided libraries.
Tested with Arduino IDE 1.8.8 using AVR Boards Manager 1.6.21.
It not work reliably with AVR Boards Manager 1.6.22 and 1.6.23 usually installed by default with Arduino IDE >= 1.8.6

Hi Werk

Sorry I should have said that I had made sure I was using v1.6.21 of the boards manager as per the other posts here. Basically I removed Arduino from my laptop and deleted the libraries and started with a fresh installation. I used all the libraries that were included in the WD software.

   

I then recompiled the software and uploaded to both the RX and the WeatherDisplay thinking that this would resolve the problem.

I will try removing the IDE again, the only thing I can think of is perhaps I missed something when removing it.

Chris