3M General purpose adhesive remover.
Had the same issue on the plastic trims from my SS when I replaced the seals for the T Tops. Dealer answer to the leaks was to pack the areas with butyl to remedy the problem.
As a different thought, try some more butyl. When I remove annoying stickers and they rip or leave glue behind, I use the sticker and tap the glue and can get most of it off. I think the same can be done with butyl. Get enough to roll into a ball and dab at he area in a fast on off motion. When I took my quarter glass out, I used the the collected goop to pull what was left off the opening. I then used it to clean my hands with. It may be too late after trying to clean it, but it may work.
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