I am sorry you have had problems with our ADC DAC Pi board.
The pins on the GPIO header we use are slightly narrower than those used on some other boards which can occasionally cause connection problems with boards stacked on top of the ADC DAC Pi. One solution we have found to fix this is to bend a slight kink into any problem pins making them press harder against the inside of the other connector.
Thank you for your suggestions on how to improve the design. I will try to add extra power pins and a DAC-load jumper into the next revision of the board.