Jim I have never had that problem and know Lightstar uploads revised skins all the time.
But I don't think he changes the preview image often. Anyway, been a long time since I uploaded. But I remember if the updated preview was named the same, it would not take. Had to be named differently. The preview, not the skin.
As example. If the original preview was MatroX DX.jpg, and I changed it to an updated image, I had to name said image something like Matrox DX 2.jpg, or the like. Otherwise it wouldn't change.
YMMV.