Body/Trim: 140: Air extractor drains

[142 Guy]

Under the rear window on my 1971 142 there is an air extractor. The air extractor has a boxed container pretty much the full width of the rear window with drains at either end. Drain hoses are attached at each end of the box and drain into holes in the hump over the rear axle. However, it is not clear where the drains actually go after the hoses are shoved into those holes. Are they supposed to drain into those formed channels / rails that run along the sides at the back of the car and exit out the back?

The reason I ask this is that last year when I had the car jacked up in front to do some work I noticed water slowly dripping out around a body plug in the floor - roughly below the back seat on the left side and perhaps 10 - 15 cm in front of the rear wheel. The plug is in a 5/8" hole. The plug is not shown in the attached parts diagram; but, the red arrow in the diagram below shows the approximate location.

I popped the plug out and about 100 - 200 cc of water came out. The hole goes into an enclosed cavity. The hole does not go straight through to the area under the back seat. I was poking around under the car this spring and it is not clear how the water got into that cavity unless it was coming from the air extractor drain. If that is the case, does anyone know where the air extractor drain is supposed to drain to and how you are supposed to get it to where it is supposed to go? If the water is not getting in there via the air extractor drain any suggestions on how the water might be getting in there?