This is not a hard problem to fix. The Nexus 7 opens easily and you only need to remove the back to access the USB port. You do not need to disassemble the unit beyond opening. The USB connector is surface mount soldered to the board. The problem is that the physical flexion causes the solder joints to break; in my case, it was a combination of force plus a marginal solder connection on pin 1. You will need a fine tipped soldering iron designed for SMT work. Pins 1 and 5 are connected to a plane, so they need plenty of heat. Reflowing the connections on all the pins did the trick for me. You need not unsolder the connector. I also tightened up the connector itself using some pliers; the housing of the connector is just crimped and it also gets loose. Good luck.