FFC (Flat Flexible Cable) ZIF Connector Reliability
I designed a product line that used the FFC's and what I found is that long cables (about 12 inches) would tend to work loose in shipping.  Basically, there was enough cable flopping in the breeze, with enough mass, that when the box was bumped around there was enough force/torque that it cable could come out of the connector.  Fastening the cable down along it's length, so it couldn't flop around so much, helped a lot. 

In the same product, we have a small LCD with a short (1 inch) FFC on it.  We have never had an issue with this one.

This product line has since been redesigned to eliminate the FFC's (except for the LCD).  The FFC's were an expensive mistake for us.