moosetrax has got it. Raise your unit to somewhere near 20 ft.
All I can tell you is what worked for me. Adding another solar panel of my own, to the existing single panel motor, and painting the unit glossy white. My sensor only goes one degree high now at the most. Some days it is spot on.
I'd take a refund if you can get it, and put it toward a meteobridge. I am now sharing with rapid fire to WU, also AWEKAS, CWOP, PWS weather sites. The Euro is low right now, so about $74 and you get the license.
meteobridge was a waste for me, I tried it but ended up going the free route with kevin's acu-link bridge software to rapid fire to WU and the other sites.
As for the height of the unit well mine is about 12 feet up but off the edge of a building I have putting it about 2 feet from the top of that building. Can you explain with a little detail of how you added another fan on your own to the unit as in some instructions and parts list?