I'm thinking it may have been that the sensor was automatically assigned an M HC at one point and retained its security code when I recently moved.
I normally right click the security modules in AHP, change the module type, assign the HC/UC I want, change module type back to its original one. I then check that the module is showing the codes I assigned using AHPs tools/Find other computers function.
I don't recall ever using HC M for a security module but where AHP auto assigns a code with OnAlert unless you change it, it may have used M for this particular one.
I assigned it an H HC in OnAlert but it still said M Unknown until I removed the batteries and then reinstalled it.
Must have had to do with OnAlert and AHP.
I was only seeing this M code when that specific DS10A was tripped.
Once I followed the steps of removing and reinstalling the batteries and then issuing another new security code, the M codes stopped.
I have just setup a fresh .ahx file, so the previous one may have been corrupt. I've also since removed the sensor from OnAlert and have mapped it as a standard HC/UC in my V572RF32.
I'm aware the DS10A and other x10 security sensors do not send a standard HC/UC which is why I mapped the sensor in OnAlert and now, instead, with my V572.
I've also seen this with an A code.
The AHP activity monitor has shown A Unknown and also A00TV.
This seems to be a stray signal or one of my devices are reading as A00TV.
I DO see this when using Windows Media Center with my Icon remotes and CM15A, but am still seeing this when I'm not using them.
I have gone over my setup thoroughly and am using an XTB-IIR and a handful of XPPFs and have not noticed any of my previous noise issues since adding these pieces to my system.
Nothing else has been added electronically and the noise was not generating any x10 codes previously, just causing intermittent module response with certain modules (more likely would have been signal suckers eg: running multiple PCs unfiltered at the time).
One other thing that may have caused an issue. I have actually had 2 sensors generate and register with the SAME security code.
Where this is so unlikely, it took me a while to notice this.
Weather this caused my issue at the time or not, I don't know.