I had a very "original" CM15 lock up and repeat code "D4" two or three times in one week - exactly as your log appears (as if there was an RF source repeating the code). There was NO RF SIGNAL - the CM15 was reporting RF received that wasn't even there. Since I have a WGL receiver - all RF receiving was *disabled* on the CM15! By monitoring my system with an 1132CU instead of CM15 and keeping my WGL receiver in place - I quickly proved there was no incoming RF signal.
In fact, it was my CM15 going flakey and artificially storming itself! I retired it shortly thereafter, but I did abandon "D Codes" in my system, and removed the batteries and let the CM15 sit for 24 hours before putting it back in service . I think it did work properly for a couple weeks after the cold reboot and change of codes, but I didn't trust it. I retired it within a couple weeks of the incident.