See the following video sequences:
This are sequences cut out from a 12 minutes flight. For those who would want to say"Bullet connectors for sure" please do not do that - how come it never twitches when it is in "loiter"? Only in "stabilized mode" and "Altitude hold" mode.
The beep you hear is an HK battery monitor indicating heavy load on the motor/motors when these happen.
See the logs also posted in the zip file attached.
Any help would be greatly appreciated.