Go to the link listed below and near the bottom of the page you will see the Glitch Reducer from Helihobby.com I had the same problem as you with two Corona 120's Lots of guys in here gave hundreds of suggestions and I thank you all but unfortunatly none of their suggestions seemed to solve the problem, So I decided to try the heli hobby Glitch reducer and I never had a single glitch since! That was 3 months ago! Besides the Glitch reducer is only $14.99, But a truly great product. Thank god for that glitch reducer, I wasn't able to fly anymore without it!!![X(] Trust me it will work, Corona 120's are Notorious for glitch problems!
It's the 24th product down from the top of the product lists.........

http://www.helihobby.com/html/extras.html