No problems with a ubec (@5v), just with reciever packs.
When you disconnect the red wire and run a ubec, isn't the "brain" potentially looking for a certain 5-0v, 1-2ms signal? What if your radio was over 5 volts, couldn't the brain not see a proper 0 volts on the bottom of the square wave?
If I could only draw what I see in my head, then afford to build it, and finaly get to play with it...