the camera works perfectly fine on two of our 640XL. Have you considered it may be your phone or your settings?
Turn your living images or rich capture off and see if that helps. If you've done that then possibly do a hard reset. If you've done that also then it might be your phone. Living images is notorious for leaving your images in bad quality if you don't know it's on. My wife got headaches from that until we realized that it was on and that she either had a moving object or moved the camera after the click. The end product is a messed up image in the photo app.
This was taken on two prior builds (10581) and there was no post processing or resuming involved.
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