Here are a couple of quick useful tips for anyone who has a Twister Hawk RC heli and has experienced the same weird, frustrating behaviour as I have.
1. Occasionally, for no apparent reason, when you try to fly the helicopter, it will just keep tipping over to one side. You can stand it back up and try again - same thing. You've made sure there's nothing wrong with the blades, the flybar, the battery or the linkages, but it still happens.
What I do in this case is pick the helicopter up and hold it in my hand, then with the other hand, I apply full throttle for a second or two, while holding the heli still. This seems to sort the helicopter's sensors out and it then flies perfectly.
2. Every few times I plug the battery in, the throttle won't spin the blades up. If I disconnect the battery and plug it back in a few times, everything works again. Also, don't move the throttle for a few seconds after plugging the batteries in. It seems that if you move the throttle too soon, the receiver turns off the throttle function for safety.
3. I've never been sure how much adjustment is required on the flybar linkage, so through trial and error I've come up with a setting of only a few turns out from the shortest length - just a tiny bit of metal visible between the linkages. Too much or too little results in the helicopter being unable to gain height.
Hope that helps someone.