I've measured the 5v0, 3v3, and 1v8 rails and they are all good. Even after the Ethernet fails I've tried a couple times to get the Ethernet back up after it goes out and haven't been successful. The only thing that seems to help is shutting it down and restarting it after a while. It does seem to h...

Long story short: My Ethernet works intermittently on my Pi. I was able to trace when it failed. The consistent pattern is that the Ethernet works when the board is cool. When it warms up, the Ethernet quits. It does this every time. I am testing this by attempting to connect to the internet and fai...