Mort,
First, Its not recommended to use the Cbox/2 receiver setup in the trainer mode.. Because it requires you to clone the second receiver, and you have to alter the setup too much.. we have said that on here a couple of times.. Its best where there is One receiver doing everything, like an R14, but then a clone can be added..
I suspect one or both issues:
In Dual path, its possible to bind both to the same receiver and not know it..
Is it possible you had failsafe enabled in one or both of the receivers?
It sounds like the Cbox went to failsafe.. So I suspect something in your receiver setup.
We have been flying jets on the Dual Path Dual Receiver setup with no issues..