This CAN still be noise issues.
Imagine, for a moment, that your CM15A is your friend, standing at one end of a long hallway, singing for everyone standing along the hallway.
The farther you go down the hall, the harder it is to hear him.
If someone takes a stereo and plays it really loud halfway down the hall, then the people beyond the stereo won't be able to hear the singing, while those close to the singer will. Those between the singer and the stereo, but closer to the stereo, might also not be able to hear.
The stereo creates noise that drowns out the singing.
Now, imagine if instead of a stereo, someone takes a mattress, and uses it to block the hallway.
Everyone between the singer and the mattress should be able to hear, but those beyond the mattress will have a much harder time.
The mattress absorbs some of the sound.
You might have both things going on at the same time.
The best way to test for this, is to turn off one circuit at a time, and see if one circuit seems to have either a "stereo" or a "mattress" on it.
If you don't find any single circuit, then do the opposite - turn them ALL off (except the ones you have the controller and devices on), and then turn them back on one at a time to see when the problem comes back.
Once you find a suspect circuit (or circuits), then turn off all lights, unplug every device on that circuit, and test. Start plugging things back in until you find the offending device. You'll probably need to filter that.
That's one way to tackle the noise / signal suckers.
Bridging the two phases might help, too. In the example above, there is another hallway connecting at a right-angle to the first one. The singer is now all the way at the other end of the second hallway, making his singing very hard to hear at the end of the first hallway.
A bridge/coupler/repeater is the equivalent of giving him a microphone, and putting a speaker at the intersection of the two hallways, where he was standing before. That might be enough to get the singing past the stereo and the mattress.
Now, a booster like the XTB-IIR (See Jeff Volp's page here:
http://jvde.us/xtb/xtb_overview.htm) does something a little different.
It moves the singer back to the middle where the two hallways meet. However, it gives the singer a loud bullhorn. The singer's voice is now loud enough to be heard over most stereos, and can get through most mattresses. Putting it in the center helps, too, since there is less distance for the voice to travel now.
(I hope my examples make sense - I ran it by my wife first
).