Yup. Friend was over last night with a Vibe 50 that just wouldn't fly right. Since I found this hard to believe (those things are like flying a Lexus) I had him pull the head and we started setup over with a swashplate leveler attached.

Turned out one of his roll servos was bad or had a dead spot, you could get it dead on level but as you added pitch one servo would wait then catch up after a small bit. I stuck my thumb on it and moved the stick and it was very easy to get it to stick.

Realizing that something wasn't right, and taking steps to address it right away probably saved his helicopter.