Thumbnails in my game are normally lit, yes. One question is: Do you see the thumbnail as bright in game as well or only when you open the package in S4S afterwards? I am wondering if emptying the cache would help in your case or make it worse (as in: all your in game thumbnails would become like this -_-). Maybe removing all your mods and leaving only the new one where you want to generate the thumbnail (having deleted it from the package beforehand via S4S) would bring a different result that would show that one of your mod is guilty. Or maybe reinstalling the game could help.
Some stuff to try out.
Please do not contact me via pm for help and simply post in the appropriate section of the forum so that everyone can see and help you there.
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