That is one of my complaints about the harness underneath the front seats, they are secured with a plastic clip. It doesn't seem extremely flimsy, but I am sure after a good amount of time it will fail to keep the harness attached due to its location.
**BUMP BUMP**
This appears to be one of the only posts about this specific issue. Although it can be caused by a few different things (like you mentioned, a badly seated connector). I thought that I would just add my experience to this as well.
I got inside of my truck today, and this...