I have a frankengimbal that started life as a Copterlabs Vortex 285 gimbal for Runcam 2. I've had so many problems with it that at this point I have replaced every single component. There is still one issue that I can't work out. The pitch axis has four symptoms that I can identify.
1 - Intermittently fails to stabilize at a level position on power-on. 2 - Has high frequency oscillation near the travel extents. 3 - Over-corrects. 4 - Skips a pole or two in flight.
I've dialed in the tuning of the pitch axis to the best of my ability. It isn't perfect, but the best compromise that I can get. Any deviation from current settings results in worse oscillation.
The other axis, roll, works like a champ.
I'm guessing that I'm not the first to have these issues, and I'm hopeful that someone with experience can share some ideas.