Thanks for the info on ISLC. I’ll check that out, but as I’m on the SU15 Beta, I want to see if I can find the cause of the CTDs that are now occurring. 
Possible causes, based on recent changes to my PC, are:
- Installation of City Update #6.
- Update of the driver to my graphics card.
- Changes to the Graphics settings in MSFS after I added a 55" 4K TV to my system.
- Installation of one or more of the Windows updates that were pushed out over the last week.
- None of the above. Something else is going on.
Item 1 is the “obvious” choice as the CTDs started happening after it was installed, but I’m not convinced that it is the culprit. CU6 did not change any core content files (AFAIK) and is basically just better photogrammetry & scenery, similar to all the other CUs I have installed.
Item 2. I upgraded my Intel Arc 770 GPU driver from v31.0.101.5333 to v31.0.101.5382.
While a bad driver can cause CTDs, I doubt that it would cause the continual reduction in memory that I’m seeing that is causing these crashes. If the culprit, I’d expect to see a bunch of CTD-related posts in the Intel A770 Graphics Card thread, but there are none.
Item 3
After installing the new TV, the display configuration in MSFS changed from:
- Two 1366 x 768 @ 60 Hz 1080p 32" TVs (1 using Experimental Mode Window) to
- One 3840 x 2160 @ 120 Hz 4k 55" TV & one 1366 x 768 @ 60 Hz 1080p 32" TV displayed in the Experimental Mode Window.
Plus
- Render Scaling was changed from 125 to 100
- TLOD was changed from 250 to 400
- Frame Rate Limit was changed from 100% MRR (60 Hz) to 33% (120 Hz)
- HDR10 was changed from Off to On
As expected, I saw a reduction in FPS both with 100% MRR @ 120Hz and obviously when capped at 33%.
The rendering of all those additional pixels & a higher TLOD impacted the FPS and might cause an increase in memory consumption (I’m no expert on this) but I don’t see why any of the changes would cause a continual reduction in memory over time.
Which leaves item #4.
The updates that were installed on 04/15 were:
- 2024-04 Cumulative Update for Windows 11 Version 23H2 for x64-based Systems (KB5036893) and
- 2024-04 Cumulative Update for .NET Framework 3.5 and 4.8.1 for Windows 11, version 23H2 for x64 (KB5036620)
- A bunch of Windows Security virus definition updates & the like.
- Xbox app & Xbox gaming services were updated on 4/11 & the Microsoft Store on 04/15.
Was there something in the two Cumulative Updates, Xbox app or Xbox gaming services that has affected MSFS? I have no idea, as I’m not an expert in these matters.
Investigations will continue…