The white plastic "shield" on the rear of my Mac Mini (where the ports are) sticks out a bit past the metal case. Can anyone check their Mac Mini to see whether the corner of the shield closest to the power button sticks out past the casing? Run your finger along it. Is the plastic flush with the metal?
I took my Mac Mini apart to clean it, and as I was putting it together, I noticed this when I snapped the cover on top of it. I can't remember whether this defect was always there, or whether it was my fault.