iPhone 6: gap between logic board and rear case?

Short version of the question:

Is there a small gap between the logic board and the rear case? Or does the logic board lie directly on the rear case?

Long version:

There is a small dent in the rear case (approximately one 10th of a millimeter) at the location of the logic board. Could that have damaged the logic board?

In my case the iPhone stopped working about 4 months after the emergence of the dent. I was updating to the newest iOS (9.3.2) and then the wifi stopped working (greyed out). Resetting, restoring and finally downgrading back to iOS 9.3.1 didn´t solve the issue so I updated back to iOS 9.3.2. After that update wifi still wasn´t working. Then I disconnected it from the computer and after a few seconds it turned off on its own. When I tried to restart it, it got stuck in the startup screen. I restored it again, wifi still not working. I turned it off but it it got stuck in the startup screen again whilst trying to restart.

The Apple-contractor, who sold me the device 5 months ago, blames the whole thing to the 4 months old 10th of a millimeter deep dent on the rear case. They came to that conclusion only with looking at the outside of the phone. No one took it apart to check if that conclusion is actually true or not.

Thanks for your help!