Are you running the 2-3s System or the 1-2? Which Model? Also, is the setting on your radio adjusted proper? My advice to you would be to reset everything back to stock/zero settings and start from the bottom up. Ive been running the New Pro Orions since they came out and have never seen that issue.
It almost sound like a Cog issue with the motor though. Ive seen Castle systems do that due to lack of power being pushed through the motor, hense the reason I asked about the esc. Also make sure your battery is fully charged. Sometimes the basics can be too basic..