I couldn't find a reason why as it is not deterministic, but some times it works, some times it doesn't.
@Alex @Matt-Ogborne FYI: the I2C ADC I am using is https://www.adafruit.com/products/1083?&main_page=product_info&products_id=1083 which provides either 4 single ended or 2 differential analog inputs.
4 different I2C addresses can be assigned to each device giving the possibility of 16 single ended or 8 differential inputs (see: https://learn.adafruit.com/adafruit-4-channel-adc-breakouts?view=all for more details)
Thank you, didn't realise the Arduino dock isn't flashed. Managed to get it working.
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