I have a new installation of a Gemini autopilot with auto trim in my RV-6. The unit works fine except for the altitude hold mode. The aircraft pitches up and down randomly and suddenly as if it is overcorrecting for the selected altitude. For short periods it appears to work normally then starts with the pitching movements. I have adjusted the vertical activity level, Tested the static system for leaks without any resolution. I have standard instruments with a Dynon D10a. The aircraft is equipped with a piper style pitot mast and two side static ports on the aircraft. I have contacted Trutrak but have not found a solution. Any assistance or ideas on how to trouble shoot and fix this issue would be appreciated.