Thanks to everyone for their input help and background with this. I finally sorted out the culprit and thought I would post with results.
Short story: Long time ago I installed a cell phone repeater amplifier thing in my attic. I had forgotten it was even there. Not sure if ever really helped much but I believe what happened was the repeater or the cheap wall wort power supply is starting to or has failed and was creating a tremendous amount of noise on the powerline. Interdevice communication was working fine but it was prohibiting communication with my PLM. Unplugged that cell repeater and magically everything came back online and communication is once again robust and reliable.
The way I found the issue was basically to shut the entire house off at the breaker panel to start isolating what was stopping communications. I turned off literally everything. I picked a device that was not working but on a circuit without much else. I turned that circuit on and started doing a restore device. To my surprise that device immediately started communicating, and restored itself, green arrow gone.
While watching the event viewer in mode 3 in a working system you should see that clip along fairly quickly with INST-TX commands followed very quickly by INST-ACK commands. It cruised along with the commands essentially continually scrolling up the event viewer, with all but two circuits turned off in my situation.
I started turning circuits on and watching the event viewer work. If it kept the commands moving I knew the circuit was not the issue, periodically I would have to re-issue another restore command on that device to keep the PLM communicating and the event viewer showing me traffic. Eventually, I turned on my garage which also feeds the lone outlet in the attic, and the communication immediately changed tone to where I would see much slower communication traffic, way more TX commands, less ACK commands, more hops, and eventually a failed communication with a red exclamation point. Turning that circuit on and off at the breaker panel would immediately change traffic behavior every time. I knew I had found it. I unplugged everything in the garage to isolate further (garage door openers, insteon switches, unplugged whatever my wife had plugged in and repeated the test. Finally remembered the thing in the attic, unplugged it and boom the world was right again.
Long story short thanks for the tips on the event viewer, had not really used that tool before very helpful.
I suspect my original PLM is just fine as well, since the whole reason i switched over was that I suspected the PLM failing was causing my communication issue.