There is another reason for the CCM to "take off."
There is a bug on some R4lC boards, If track power is brought up slowly with a chopped wave supply, the CCM will boot up before the radio board does. The CCM will think it is in conventional mode.
Try applying power instantly, like AIX1,9 with a TPC or Legacy Powermaster, or applying track power and holding the track direction key down for a few seconds. Do that before addressing the loco.
That might work.