Pro XC racers often like a responsive bike. 'Twitchy' in the hands of a pro is fast. My guess is you are used to the 29er and the new bike is a 650B - 29ers like straight lines and turn like beached whales. If you are used to a 29er, anything remotely responsive will feel twitchy and take a bit of getting used to. I had the opposite problem moving from 26 - 29er - same end result - crashes and swearing for the first few rides.
There are things you can do nothing about -geometry, wheel size, things that cost a fortune to change - fork rake, and low cost fixes. Low cost fixes I would look to first are stem length (Increase to reduce responsiveness) and wider handle bars.
Tires and tire pressure.....
Zero cost fix is to keep with the bike till you get used to it...
Play with shock set up and tire pressures and see if it helps. "Twitchy" could be too much rebound (not enough rebound dampening) - are you experienced enough to have a feel of how the shock/tire/track interactions are working?
Its really hard to provide an answer as there are so many things we cannot know about you, the bike set-up, the trails you ride etc. In the end the fastest way to a solution is visit your LBS and get a bike fit, explaining your problem. A good bike shop will be able to sort you out, or at least, tell you what is wrong.