Some people advise against this but I like checking general heli behavior while holding it up by the skids and giving it throttle. If you do decide to do this, be safe. With that out of the way...

• Does it look like your servo arms are moving smoothly throughout giving it throttle? Does it look like it suddenly pulls down all of the sudden instead?
• Are your servos glitching or sticking at any point during cyclic movement?

With power removed from the main and tail motor:
• Is your blade pitch at zero while at 50% in Idle Up mode (another check in addition to the 2°)?


EDIT: Oh wait, you have the DX6 right? I think someone with that knowledge should chime in with other troubleshooting tips.