i'm on the 32bit board with the newest firmware and when i activate the follow pitch mode i get some strange behaviours. When i pitch the camera forward, the yaw turns the camera to the left, when i pitch the camera upwards the yaw turns the camera to the right. That happens also when i use the Frame imu or without.
I have no idea how to do 6 point calibration accurate enough (without some very accurate cube that I do not have), so I have always just done 1 point calibration, works great.
But probably this is something else too. I had similar issue (between roll and Yaw) and performed EEPROM erase (all settings will be erased) and performed complete setup from start making sure all steps followed and now it works much better.