I don't know if many folks are working on Moonroofs/Sunroofs but thought I'd add what I found. I have been working on the Moonroof on a 1995 940 I bought a couple weeks ago. After replacing the switch and motor from a parts car, the moonroof now works but after checking the channels for drainage I found water coming down not only under the pillars but also the rear of the headliner on the sides on top of the rear pillars.
I removed the 3 plastic buttons holding the rear of the headliner and the clothes hooks from the side and could pull down the headliner on the sides. The drain tubes were connected to the channels with zip ties and were leaking there.
I replaced the zip ties with hose clamps and that seems to have fixed the leak. Here's a picture with the new hose clamps:


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Mine:5-940s running, 2-740, 1-940 parts, dtrs:4-940s