hello gbduino,
I see that you are using a 2V battery. I'm not sure this voltage is in the working range for ADC.
In the case of normal power plug, this is another matter:
From what I see in the schematics, the AVREF is either 3.3V or external source. Did you plug an external source?
Furthermore, the wiring_analog API is providing raw access to ADC inputs. Did you implement a calibration in your sketch to ensure the values are processed correctly?
Anyway, I don't think that your issue is covered by the Errata.