Not sure if I know the point of your post either, but another option is sending your N5 for RMA first (that way there's no hold on your account at all) and wait for them to send you a new one. You can even buy a moto g use it for the week or two you won't have a phone and return it or something.
I understand that you're trying to see if anyone knows what's wrong but to me it's like a needle in a haystack. You're going to be opening up the device to look for a loose connection, but it could be something completely different. Maybe it's a hardware part that is malfunctioning in which case you would need to track down a replacement. This is why everyone is suggesting you just RMA because, speaking from experience, it really isn't a bad experience at all. If you really want to try and fix it yourself of course you're free to do as you wish since it is your device, but I highly doubt anyone on the forum will be able to say for sure what the problem is.