[JRTJH]

The holding tank valve "cable system" is a Bowden Cable. What that means is that it's a single wire run through either a "spring type" or "hollow cable type" structure. Look at the handlebar brake cable on your bicycle, the speed control cable on your lawn mower or the thumb actuated accelerator cable on your ATV. They all are "Bowden Cable" systems.

Usually they are a very reliable system, but pulling them too hard can break the plastic valve seat, installing them with a "kink in the cable" can make them difficult to operate and rust/corrosion will make them impossible to function. If the outer cable structure is not secured to the frame, the entire assembly moves, which makes opening the valve "impossible".

Take a look at your system, many don't have "cable slide valves" and yet they get blamed for "cable problems". Often, debris in the valve seat/seals, kinks in the cables or rust/dirt in the sliding part of the cable are the problem.