A few weeks ago, I had replaced the original black back cover with a new white cover. /r/Nexus5/comments/4ms40p/looks_like_new_with_a_new_back_cover/
Yesterday, I did some spring cleaning and now looks like new and it feels like new.
cleaned up the micro-USB port because the cable kept falling off. I used a x-cutter to make shards of wooden cocktail picks in order to remove all the gunk inside the port. It took about 10 minutes.
disassembled the phone and cleaned up the power button by following the instructions from this video. https://www.youtube.com/watch?v=doPuXkQTGbc. Although I used the switch cleaner on the power button, I think the problem was all the gunk that had also accumulated on the outer button.
After reassembling it, the vibration and the NFC was not working, but this had happened before when I had replaced the back cover. This is basically the back cover contacts that are not touching properly. My suggestion is to remove the cover and close it up again from the bottom to the top, using your thumbs to press the cover into place. To really put it into place it feels that you may make too much pressure and break the phone. So, make sure the phone is in a flat surface on top of a towel, in order not to scratch.
For UK users, here are the sprays that I used to clean the phone:
As always, do it at your own risk. I felt confortable enough I actually know about electronics. However, things could have gone wrong. One of the things that videos rarely mention is that you should ground yourself when touching any electronics.
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