Without being there in person, it's hard for me to tell exactly where the problems are --- other than they seem due to the contacts on the ribbon ends --- and their corresponding contacts inside the board connectors --- not being properly aligned AND not pressed together hard enough to make firm electrical continuity. These interfaces carry very low voltage signals with miniscle currents, thus highly susceptible to corrosion, debris (dust) & indexing assembly.  On some boards I've worked on, I've actually had to scotch tape the ribbon on the board to hold it firmly in the connector, then devise a thicker wedge from a piece of credit card to assure contact enough pressure inside the connector.  Jack E/NJ