Bonjour visibility dropping over ethernet only

I'm using a recently purchased 2012 Mac Mini and installed the latest Yosemite. So far, it's being used headless as an iTunes server and I also have OS X Server 4 running on it for some basic home server stuff.

I'm using the Finder's Screen Sharing to log into it. This works fine over Wi-Fi. However, when I use ethernet, it will work for a while, then just drop out of nowhere. I'm guessing that Bonjour is dropping as I can no longer see the Mini in the Finder server list. I haven't been able to find a pattern as to why it is dropping yet. I have to hook in a keyboard, mouse, and monitor; then re-enable wi-fi, and it pops up in the list again. I would rather just hook it into my Airport Extreme using ethernet and leave wi-fi off.

In iTunes it also drops out of Home Sharing along with the Finder view. I've tried 'Connect to Server' using the IP, and nothing.

Any ideas on how to proceed?

Thank you, Glenn