"Now I know there is a special hose that is hooked up to the a/c that discards the waste, can this come undone in flight? "
Yes, it's hooked up while on the ground. The dump hose is attatched to the lav truck and is not part of the airplane so it cannot come undone in flight. The cap to the drain valve is subject to leaks and that is where the problem occurs.
Also, the culprit aircraft is rarely identified, so how can one be sure it was a Boeing???? In my day I have dumped Airbus, Boeing, MD
& Lockheed and they can all leak if the plug seal from the waste tank to the drain line is bad and there is no secondary stopper at the drain valve opening (or it leaks too).