This certainly looks like a problem between hop 1 and hop 2. You mention that hop 1 is your ISP, then it looks like there is some problem with the connection between those two devices.

Powerline-provided service is something we've not seen much of yet, so it's difficult to comment on the exact problem.

If 192.168.120.1 is a device inside your physical location, then you should certainly check to make sure the connection between your wireless gateway and that device is solid.

It may be, however, that the 192.168.120.1 device terminates on the other side of the powerline, in which case you should contact your ISP and ask them to help you troubleshoot. If you change your "Samples to include" to something more like 500 or 1000, the packet loss percentages will probably show a lot more consistent story and you can paste a graph into an email and send to your ISP's support team.

- Pete