Could be.  Ive not had any OWB issues out of my EXI helis...the 450 or 500.  Both are fine stil.  But you could be onto something.

I noticed the OWB on my CX250SE was cruddy and I had to take the 250 apart and clean it when I was lubing up the bearing and loctiteing everything.

Its definitely gonna be one of those things that the OP will just have to start swapping out things one at a time till he figures out which part is the culprit.  It doesnt appear to be a "settings" or "gain" issue to me.  But like Ive stated, gyro setup is my "weak point".</p>