Strange behavior of ADC values

Hi.

I'm testing the ADCs on the SK-S7G2 board because we have unstable ADC readings on our custum board.

I put a stable voltage on pin P00 (battery voltage).
I noticed that if that ADC reads more channels (in this case 3) the reading error is about 8 channels instead of 3 if I read only one channel.
And the error is only in the first readings then the value seems to stabilize around 1 channel..

I don't understand if I'm doing something wrong or if there is a bug in the function.

I attach my example project.

Thanks

Paolo

SK-S7G2-Test-ADC.zip