Well I still love my old 2.1 HW with 2.1.5 FW OpenSprinkler but yes I noticed a good while ago that the Zimmerman correction stuck at 10% without any variation due to changing weather station.
I noticed that in the “System -> Location” there was my old “pws:ILAZIORO38” wunderground meteo station (which sits on the building in front of mine be they always blessed 🙂 and I have used for years.)
I click on it and via the map chose my home address which has now changed to another known location. Submit.
Now the homepage shows the right meteo conditions and the watering percentage is back to something sensible.
Could you maybe have the same problem?
PS Why is it not possible to use the old Wunderground PWS meteo station names? The one I used is https://www.wunderground.com/dashboard/pws/ILAZIORO38 and still exists and works flawlessly but I cannot find a way to input its name anymore.