Hello and good day AlpineDronesEu. I am sorry for the trouble and thank you for reaching out. Are you able to post a sample footage of the said issue for us to see and to be able to assist you further. In addition May I know if the firmware of your DJI Phantom 4 Pro is on its latest version and please try to calibrate IMU and do gimbal calibration to see whether the issue remains. Please keep us posted on the said issue for us to be able to help you further. Thank you.
"wavy video" could be intercepted many ways, best to upload a vid. For my previous issue with choppy video feed i had to update the drone firmware. Did the trick. I've found i need to update the firmware after any DJI app update.