Sounds like some load is coming on that is blocking/sucking signals. One way to test is to turn off one breaker at a time and test to see what circuit has the offending device. It could be a TV, PC, printer, phone charger or LED bulb and then add a filter to that device.
Have you tried locating the PLC01 or the P2 at the same outlet as your old CM15A?
X10 signal integrity is a matter of "raising the bridge (signal strength) and/or lowering the water (noise/suckers)" which is why a good phase coupler and amplifier/repeater are keys to success along with a filter or two.