I think these other recent posts may be describing the same issue:
This week I’ve had issues loading back into the Brazil challenges if I try to restart them after crashing or pulling a bad score. I never had issues with challenges in the past, but the Rio area is denser than most challenge locations. I also had issues loading up a banner towing mission in the SoCal area.
I haven’t flown many missions since SU1, but it was never an issue pre-SU1. The only other change was I temporarily changed my settings from Ultra to Medium when I was having performance issues last week, then changed it back. Ultimately, reducing the LOD from 200 to 100 let me restart the challenges successfully. The performance issues seemed to be due to some kind of memory leak, which obviously isn’t related to this issue.