I also note that the adhesive binds to an area that is much thinner along the left side too. If so, that might be considered a combination of a design defect and a manufacturing defect. Furthermore, my first one had a serial number of C60K, and the second one of C80K so manufactured later, but with the same defect.
http://forum.xda-developers.com/showthread.php?t=1853154
So, back goes Nexus 7 #2. I must say though, this unlock/root & unroot/relock process with that Nexus Root Toolkit has almost become second nature to me. :\
I got number 3. Also C80K. The left side is ever so slightly higher than the right, but so far not spongy. Fingers crossed.
BTW, my first C60K had slight differences in the packaging. The sticker on the back with the serial was unreadable, because the font was black. The two C80K units had white lettering for the font.
Also, the C60K's packaging sleeve was much harder to open. It was so tight I had to use one hand on each side, sliding down the sleeve while the interior box was held against a 3rd object. That one had two pieces of tape inside, sealing the box.
For the C80K boxes, the sleeves were still tight, but loose enough that I could remove them normally. I noticed the inside boxes were sealed with only one piece of tape.
Minor changes, but nonetheless it seems things are being modified on the fly.
P.S. The place where I returned the 2nd defective Nexus 7 said that they had already been warned by the manufacturer that there was a screen lift defect, although there was no recall issued. Furthermore, that single store said they'd already had a bunch of returns specifically for this issue.