I saw that post, and thanks for it - none of my dozen or so have the problem, but now I know to look out for it, so 'ta. Could you explain the "flat spot sanding", please? I can't picture what you're doing, where. I remove the cup seals from mine and so it's the one drawback they have for me - not so portable. If only there was a way to combine the vaping experience of the visions with the perfect portability of the Sapphires! (I have seen an interesting looking mod on YouTube that cuts the tube down and alters the mouthpiece to use as a combination mouthpiece and cup seal, but haven't tried it yet).
ummm try this - take a large nail file and hold the cup seal against it so the 2 edges of the half round cutout (the fill hole) are even against it and then sand it so its flat instead of a cutout. it will look just like the seal in a micro stretch. i'll try to get some pics soon ...