Just a long shot, but I have had several of those and the majority of time I get funny readings or there are a lot of missing data display areas, I have swapped out the 6 v. battery with a new one (not too expensive, I got mine at a Fleet Farm store in the fishing area). I fully charged it before swapping it out.
I wish I knew more about the circuit, but there are apparently many different versions of the boards even though they all interface with the same sensors and solar panel.
I suspected my solar panel wasn't putting out the charge/voltage and that still may be, but during the spring/summer/fall they run OK.
If you haven't replaced the internal 6 v. battery, it is worth a shot and may help.
I agree, there are a lot of older stations from Rainwise so it is sad to see that service or tech help on the phone isn't available, or at least easily. The last I spoke with Brian or whomever it was there, I was basically told that repair and service was not going to be available as they moved on. I hope he was wrong, but if it wasn't a part listed on their web site (like R/H, temp sensor, or wind, or such) there was a good chance he couldn't do anything with it.
Let me know if this kludge fixes it or helps at least.
Dale