For what it's worth, after close inspection and careful (neighbor) cat hair removal, I seem to have three. If I start measuring from the side that has the charging port, mine appears at 33, 57.5 and 139mm. Here's a closeup of one of them:
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Apologies for the weird angle, it was quite hard to get the light just right, to, at all, make the crack visible. We're looking at the front edge of the Gemini lid, with the top cover removed. The white hazy part to the left is the serial number sticker.
While they are very thin, I can feel them with a fingernail, and with the top cover removed, prying gently with a fingernail, I can make the one on the picture above flex ever so slightly, so they are indeed real. I notice that all three of mine are near (but not exactly at) ends of the four magnets keeping the lid closed. I would presume the magnets are press-fit into place and that the cavities receiving them are supposed to be really tight to ensure a snug fit. Molding plastic to very exact dimensions is tricky, so maybe some cavities got a fraction of a millimeter too small, or, possibly, some of the magnets were a hair thicker than specified.
In either case, I agree with Eldkatten, the affected material likely won't see any further stress. Given there's plenty of plastic behind the magnets, I don't think the cracks will affect the structural integrity of the lid in any relevant way, so, at least in my case, I'd write them off as manufacturing blemishes. While naturally undesirable, I'm neither surprised nor upset. I've seen worse from far more experienced brands.