probably is the ribbons, where ID in IDC happens. (that's Insulation Displacement)
In other words the connector is loose where it crimps onto the cable.
you can try
1) reseating the ribbon into the connector by pressure as if you were making it new
or
2) put a new connector on the ribbon. A small vise is useful for this, get a few IDC connectors of the correct size and practice first. (on another piece of ribbon) You loose about a half inch of length, meh.
Cheers
Alan