I've had an ongoing leak into a very specific section. After lots of trial and error, I concluded it's not the drains but rather must be some sort of sealant between the black plastic channel and headliner. There is a sort of inset area along the front/side about two-three inches back that's hard to capture in photos, where a strip of fabric has come undone (photos attached). Is this an area where there is now a gap? I'm in no position to remove the sunroof, rails, etc, but this portion where I'm convinced the water is entering is under the bottom sunroof track/rail.
I purchased Eastwood flexible caulk sealer, which seems like mastic; it looks like licorice and is permanently gummy to provide a watertight seal. If I place it where the fabric strip used to be, up under the bottom metal rail against the black plastic channel, will this cause disassembly problems in the future when the headliner is replaced and the sunroof cartridge/frame may need to come out? I can't find any photos anywhere on the web that show just what I'm dealing with in that area I can't see. I don't know if the black plastic channel is supposed to detach from the rails with relative ease, which the mastic would complicate if stuck to both--but maybe some other sealer was used behind the fabric that deteriorated.