Thank you. I downloaded the log from my CM15A and see the following:
See line 166. Is this the phenomena you are discussing as I am not using any RF. If so can the RF be disabled by removing the antenna or some other means.
166 1/16/2016 6:08:57 PM Receive RF A Unknown
167 1/16/2016 6:08:57 PM Receive A Bright 10
...
188 1/16/2016 6:09:10 PM Receive A Bright 10
While that's a bit different than what we saw years ago, we didn't have a log from either the TM751 or RR501.
It appears the strong 120kHz signal on the powerline is causing the super-regenerative RF receiver in the CM15A to break into oscillation and the CM15A is interpreting it as 'A Bright' which then gets repeated ad infinitum. It does appear to be the same phenomenon and, again, would seem to be related to the same poor programming with the CM15A assuming any continuous RF is a dim or bright without actually examining the actual bits transmitted.
The antenna is not easily removed and removing it may not solve this. Removing the RF receiver should solve it but that means disassembling the CM15A. You can see what it looks like here...
https://www.laser.com/dhouston/ImproveCM15A.htmlalthough I had replaced the antenna with the BNC connector at bottom left. The RF receiver is the one with the white wire from said connector. There are three leads to desolder. You can reinstall it later if desired.
However, first try unplugging the CM15A during a signal storm to see if that does cause it to stop. If not, we're on the wrong track.