I have a Blade CX which I've been having a lot of fun with, getting to where I could hover pretty confidently including nose in, and fly around my office between the cubes.

Yesterday I broke the plastic hub which holds the upper blades, and replaced it with the metal repacement hub. At some point after that I noticed that the heli now swings around like a pendulum while hovering, rather than staying in one place. Specifically, if I take off and have the power set so it stays level, and then take my hands off the controls, the heli will gradually start to move in a circle, but with the nose pointing in the same direction. The diameter of the circle increases until it's about 5 feet. In forward flight I also notice that it seems to be gently lurching forward instead of flying at a steady speed. (For those that don't know, the Blade CX is a coaxial rotor chopper, and normally will hover pretty much hands off once it's trimmed.)

I have performed the upper blade tracking adjustment as described in the manual, but this didn't solve the problem. Does anyone know what else would cause the heli to behave this way? It makes it pretty much impossible to fly through narrow spaces like a doorway, which I was able to do before this started happening.

Adam