Hi!
I had X-Plane 10 running on Sierra perfectly fine. My purchased aircraft (from multiple sources) and all scenery packages were fine.
I upgraded to High Sierra and now some aircraft and the scenery are almost unusable!
1) Severe performance degradation. Lagging, frequent pauses and autopilot not working.
2) A box/frame is appearing around the cursor when moving around the cockpit.
I have attached some photos of what is happening. When using the built in screenshot method on OS X the boxes/frames are NOT appearing on the screen shot so I had to use my phone to take a photo.
This leads me to believe that it's a graphics card issue or perhaps X-Plane 10 isn't playing nice with High Sierra?
Mac specs:
Late 2012 27" iMac
3.2GHz i5/16GB RAM/OS X High Sierra 10.13.3 (17D102)
Nvidia GeForce GTX 675MX 1GB