honestly if it isn't messing with your cyclic, and only the collective, chances are it's not electronic or glitching. For it to be electronic they would all have to be glitching, and all at the exact same time and in the same direction at the same speed. Something that given the nature of electronics is not very likely at all.

One other thing to check if you are sure there is no binding in the head, check out the mainshaft collar and make sure that it is well seated and the main shaft doesn't go up and down. ALso check the screws on the mixer arms and make sure that they are not too tight. when you flick your flybar it should bounce up and down 2 or 3 times if it's got a nice loose motion.

About the cp+ vs the pro, it might not have a seperate recever and 3 in 1, and the other thing might be the transmitter. The pro Tx has a pitch curve knob on it and also a ch5 rotary knob.