@MxD ,

Powerline networks are always finicky, and the behavior most likely has something to do with the disconnecting node. Powerline nodes all communicate together, so taking one out of the equation may be causing them to reconfigure their entire backhaul. Saying that, the Decos should be able to seamlessly change their backhauls to use a wireless connection to overcome the instability - how spread apart are all of your nodes?

While the one from the outhouse is too far to optimize its connection, can the other nodes switch to a wireless backhaul?

You may try removing the outdoor node to see if the behavior continues, as mesh nodes and even powerline are not really designed to be used that far apart.

We normally recommend keeping powerline Decos on the same circuit to increase the throughput and stability. I would try to make sure that your nodes can efficiently communicate with each other, and that the powerline signal is not being 'forwarded' through the outhouse's node.