This may not be the cause of your leak, but the symptoms are exactly the same as I had in my TW. Somewhere in the old girls life a front segment was replaced using explosive rivets and a peculiar white sealer. Water would also infiltrate the wing window and run down inside the shell.
Everything looked original from the outside until I started taking things apart. 70% of the rivets had loosened up. Every winter the shell would expand and contract undoing what I thought was a good repair.
You might not like this part.
I removed all the rivets on the upper seam and loose ones on the lower part of the segment and removed the wing. Cleaned what I could, squirted a good bead of Tempro between the panels and replaced the rivets with Olympics.
No leaks the next winter.
Hopefully your leak won't have to come to that,
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