I've had several problems with certain types of cable ends going into the FC. Some cable companies, including a few expensive ones, have changed the shape of the tip of the shaft slightly, claiming it helps make a more secure connection.
This might be true for certain types of jacks, but is not true for the FC. With these cable types and the FC, it seems that the slight weight of a straight connector coming out of the jack helps keep the connection solid, most of the time - although when I really whack an open D, not always. But the angled connection with these new type of cables doesn't have the same leverage and IME is more susceptible to vibration.
I have been using cables with Neutrik connectors for years, and their more conventional design doesn't seem to have this issue with the FC jack. I also like the straight connector, as it keeps the cable from rattling against the top of the bass.