I have this EXACT same issue with my Yamaha receiver. It worked great for many months and then all of a sudden it started doing this and it keeps doing it over and over again. I can see the light on the switch port that the Yamaha unit is connected, and it will come on blink for a few seconds and then just drop off. When pinging it, it’ll ping fine anywhere between 5 and 9 times (usually 6) and then pings stop responding until a few seconds later when the cycle repeats itself. Same things happens to both wired and wireless connection on the yamaha.
From what i’ve read on the forums, the Vera is very chatty on some protocols on the network, and likely when the Yamaha system gets its IP address the Vera nails it with unexpected traffic which causes the receiver to drop off.
The yamaha worked great for several months for me, and then this started happening. It happened right around the time I added my sonos to the network so i had originally thought it was something to do with that. But after trial and error I had made the assumption is was probably the Vera itself doing it.
Although I’m sorry to hear that you’re having this problem, I’m kinda happy that it’s not just me or my receiver!