I just noticed this last night and am curious if any of y'all have seen this...
The Kevlar back has a large spot in the middle that a little darker than the rest. Like, the Kevalr has a sheen to it and this spot in the middle that is kind of large, doesn't. It almost looks like a wet spot, but it's not.
Is the Maxx new? Have you taken off all of the protective covering?
There is one on the back, and it is very hard to see, unless you are really looking. If you haven't taken it off, then you may want to, or you can wait until it is apparent. Mine started to bubble a little after a week or so, and I started looking and noticed that it was a protective covering.
I know this is an old thread, but just bought a razr m and saw this spot on the back of it and was doing some searching. found this and wanted to reply and say i have the same exact spot. wipe it off and it goes away then appears again. almost like the battery heat is causing discoloration of the kevlar. this may be hard to see but hopefully this is proof that at least two of us are not crazy.
That looks like oil from your skin. Like where your finger/hand sits when your holding the phone. Kevlar is a bunch of woven fibers, so I would expect if your carrying your phone naked, everyday contacts will leave their marks. It doesn't look like a flaw or damage. I have a Maxx and an M. Usually in cases. Looking at the naked backs, I don't see anything that doesn't wipe away.
Ok, I am not crazy then. What is really strange is i thought about it being where I held it and getting oil from the hand/fingers into the weave of the Kevlar too so i took some alcohol and wiped it off. and it was gone. here is where it gets weird. with just sitting there and not touching the phone on the back, it came back.... tell me that is not strange.