I also have a TM751 on the same housecode, don't know if this is a problem or not, but nothing seems to work without the TM751!
It would be my guess that:
1. ... your CM15A sends the RF ON...
2. The TM751 also hears it... and transceives the signal to PLC.
3. The CM15A hears the PLC and
4. See number 1
That is a classic loop.
From what you have described, the TM751 is triggering a macro, which I'm finding difficult to wrap my head around.
I have a second TM751 on a different housecode that is set up the same way, except instead of an appliance module it's the TM751 itself that a macro turns on/off by RF and it does NOT keep sending the RF signal in a loop as you have described it here.
In any case, is there a way to stop the constant RF signal?