Cured resin falling out of glass

So, I’ve read and re-read that resin does not shrink in cold, and that resin does stick to glass, but my resin is proving difficult. I’m pouring resin into the underside bubble of wine bottles that I’ve cut to use as a tumbler. The resin sits and seals perfectly…for a short time. After a while of using the glass with iced drinks and hand washing with mild soap, the resin falls out of the wine bottle bubble bottom. I am planning on making these tumblers first friends and family, but I can’t have the bottom falling out, even if it is a “Only” decorative piece. I’m at a loss, and could use some help and suggestions. Thanks!