I twice fixed missing channels in my DL32R by pulling the ribbon cables and treating the connectors with Deoxit. Be aware that there are two connection points at each end of a ribbon. One is the connector pin that mates to the connector pinon the board (that one's obvious), and the other is where the cable connector has been crimped onto the cable. The invisible end of the pin is shaped like a V and pierces the plastic ribbon to contact its conductor inside the ribbon. So check that the ribbon cable is well-seated into its connector, and pushing the ribbon firmly against the connector can help.
I am very disappointed that Mackie would use a ribbon cable for sensitive analog signals. A ribbon cable is designed to convey discrete 5V/0V digital levels for computer bus applications. Sure it may work, but clearly it is not reliable. I lost a lot of confidence in Mackie when I saw that. But otherwise the DL32R is a great unit, so I'll keep it until I discover a functionally equivalent competitor.
