I just purchased a Sigma 30mm from B&H for my GX1. Attached it to the body today only to find 2 disconcerting issues:
1. when I move the camera I hear something moving inside the lens, and
2. with autofocus on, the lens seems to have a mind of its own and I end up with a totally blurred image (once again hearing the lens mechanism moving).

Any idea what's going on? Or should I just return the lens?

For Number 1, read the instructions that came with the lens. It's perfectly normal.

I can't help with Number 2. Sorry.

I think you only have to try another lens, it's hard to blame the GX1

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Generally Sigma lenses perform very poorly in terms of AF on m4/3 cameras (even more poorly than other 4/3 lenses). So I'm not surprised you're have problems with AF.

The noise you here when moving the camera is most likely the aperture blades opening and closing as the lighting changes. This is a fairly common issue with faster lenses on m4/3, though I've not heard anything specific about the Sigma 30/1.4.

I think you'd be much happier if you opted for the native Panasonic DG 25/1.4, although finding a store that has one may be a bit difficult (they're in short supply). The 25/1.4 has excellent autofocus and the 'chattering' of the aperture blades on Panasonic bodies is quite rare.

Also, I don't think this thread belongs in the B&H section, as your question is about the lens, not about B&H.

DH

Aye mate. I have this lens

1. It's the magnetized glass inside which lines up which the rest of the glass inside the camera powers on (this causes the lens to display an image from power up in a delayed manner, a few seconds lag)

2. I haven't had any of that. AF is quick and snappy. Accurate too. Haven't had any of the focusing issue (which is sigma. Sometimes you get apples. Sometimes a lemon)

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The loose elements are normal. As for the focusing, I find it very fast and accurate unless you are trying to do close focusing, i.e. flowers. Then it is a pain in the butt.

First of all, thanks for the reassurance about the moving elements in the lens. It's new to me so I'm happy to learn that it's not an issue.
As for focusing problems, they seem to be related to specific conditions which I learned about this morning when I spoke with a B&H salesman after trying to capture a shot of an amazing mass of tadpoles herding together like a flock of sheep. I wasn't able to focus on this image and was told that this camera/lens combination will not always work in water or low light.

I wonder if I would have been able to focus if I had turned off AF. Wish I had thought of it earlier today!