Cheryl, thanks for the update! Did you ever get a chance (on a sunny day) to compare early morning readings with midday? I also have a single panel unit and get a spike in the morning when the sun hits the station but is too low in the sky and too far north to hit the solar panel. This lasts for a little over an hour, then the panel gets enough light to start the fan and things begin to stabilize, and get more accurate.
Here is a chart from this morning that shows what I'm talking about: