Okay, this is getting ridiculous. I own a PM2 which works fine with its plastic 14-42 & 40-150. The metal-backed Panasonic 14mm and legacy adapter also mount fine. The 20mm I ordered from Amazon, however, is so super tight it feels like it's going to break the camera mount (thread here). So, I ordered a new 20mm from Amazon and the SAME THING happened! I have an old body I don't care about and forced it on and again I saw little shard of metal had fallen off the lens where the fasteners are. The serial on the first one is BR3DF002910 and the second is BR3AE001541. I don't know if that means they're from the same or a different batch but either way I'm shipping them both back back to Amazon. If I didn't want this lens so bad I'd boycott it. But I'm going to have to order a third one, this one from Panasonic, to see if their stock is a better fit. I would go used with one that I know fits but I can't see paying $275 for something that's $330 new. I might have to though if the one from Panasonic fails. Since I'm the only one having the problem I'm assuming I got some from a bad batch. Either that or there's something wrong with my camera.