A few months ago, I ran into this problem on my website where the client was not getting the entire files served from my server.
I discovered that the problem was related to Nginx having some sort of caching issue, and a simple Nginx restart fixed the problem. The errors indicate that Nginx is trying to open a file that doesn't exist, and I'm not sure whether this file should exist or not.
In the last week, this problem has happened twice again, but I can't find anything when googling the errors - which aren't particularly Google friendly in the first place.
I only have a basic understanding of Nginx, and I'm not exactly sure where to start. Any suggestions?