New to X-Pro - common issues?!

We're all quite savvy here so I think you'd be better off just posting unmodified full-size shots rather than resizing, sharpening, etc — otherwise you'll just get the inevitable 'wouldn't happen in normal conditions' responses.

Based on your photo though, if that's what you're seeing when taking a picture of a plain wall and it's not a foreign body on the sensor or lens, that would worry me a great deal and I'd definitely order a replacement. What've you got to lose? If it affects them all you'll get another one with similar characteristics and can move on, if not you're sorted.

That blotch might not be especially conspicuous on many photos, but that's simply because it's being masked. That seems like something that'll definitely be noticeable in certain kinds of shots, and while it can be cloned out in Photoshop it's not really something you should have to accept for brand-new equipment of this calibre.