Hello,
Under the slide, there will be two junction boxes fastened on the inside of the outer wall. One is for d/c powered lights and the other is for a/c lights and receptacles. Normally there are coiled cords that go in to these boxes and expand and retract with the slide. I see the majority of this problem being bad connections in the boxes. It could also be possible on your unit that you have EMT conduits that fasten to the outer wall and rides back and forth under the belly of the RV. No matter which type that you have, there will be a junction underneath and I believe that your problem will be found there. It is also possible that the cable has been damaged so inpect carefully.
Make sure to unplug the shore power before you crawl under to do any work. There have been many fatalities from someone laying on the ground and getting in to a/c voltage.
If you get under there and see something different from what I described, let me know what you see and we can take it from there.
As for drawings, they are nearly impossible to find and most design drawings do not reflect the actual installation.
Thank you,
Ronnie