Problem on ADC pin 19?WiPy 2.0

[panos29]

Hi,
I'm sampling 8 different sinusoidal signals on all 8 ADC channels . All the ADC channels are giving me what I expect, except for P19. I had a problem with P19 both when I had my circuit on a breadboard and now on a PCB, where P19 is routed to a different output. The circuitry is identical to the one that the remaining 7 channels, and indeed the output of my circuit is what I expect it to be when P19 is unconnected to the output. When I connect P19 to my circuit however, the output gets distorted. If i connect that same output to a different ADC pin, it is still fine. So somehow, P19 seems to be causing the problem.

Could this be a firmware issue?

Thanks