That reasoning doesn't mean there were hardware changes...your E71's could have had parts that were sourced from different OEMs or the tolerances in the camera sensors were slightly off from each other. I've seen a few different E71-2's from build weeks of 28, 29, 30, 34, and 35 with different product codes...they're all pretty much the same. The only differences i found were, screens that were more flush, keypads with more resistance or mushier, one had a green line near the top of the screen in camera mode, dust under the screen, one had a louder speaker, etc.