"OK thanks Leonard, I saw his initial comments about some motors nearly stopping. But yes there looks like a lot of compliance between the airframe and the extended mass of LiPo/Camera based on the photos/video. Thanks again. Richard"
"You probably have the answer to this already, but you can search for "autotune esc sync issues" to find a complete explanation of the issue. Also the Marco Robustini sync problem video at https://www.youtube.com/watch?v=0lRTN5o4UCM