I had posted a question as to what would cause the Blade CP to rotate around the main rotor and the boom control to be ineffective. I tested the voltage at the rear tail motor and it was correct so the 4 in 1 was ruled out. Bottom line, these little motors wear out. They do not necessarily stop spinning; just don’t spin at the required rpm to maintain boom control. The tail motor was replaced and the chopper flies great, once again!