Hi Lammert,
Sorry to hear this. I’m checking on the calculated GSD issue.
Right now, you can’t control the speed but adjustable speed is in the works. I would also try a faster microSD card if possible.
Finally, per this thread, some users have reported much better results by switching their camera settings to manual, which you can do in the DJI Go 4 app first: New Releases: iOS app support for Phantom 4 Pro and Inspire 2