Hi guys and greetings from Split, Croatia.
Just bought a Series X a month ago.
At first, photogrammetry worked fine, but in the last week or so I’m getting substantial stutters and lagging when flying above cities like Paris or New York.
The flight is perfectly smooth at well over 30 fps, but every 5 to 10 seconds I get a 0,5 - 1 second stutter, as if the scenery is having trouble loading, or something.
My running cache is set to 5 GB and my connection speed is 200 Mb/s.
The problem is so bad now that I switched the photogrammetry completely off. 
Btw. everything else is running smoothly and with no problems. Only the photogrammetry cities are having issues.
Also, in the last week or so, i got a couple CTD-s after ending a flight and trying to go back to the main menu. After the CTD, I have to wait for about 5 minutes for everything to load back up. Is the problem perhaps caused by that “quick resume” functionality of the Xbox? 