Getting better FPS at Ultra vs High?!?

All of the sudden, MSFS is crashing to desktop every session. I’m lucky if I can get 30 minutes of flight time before CTD. In my efforts to figure out why this is happening, I realized my CPU/GPU are giving me 15-20% increase in FPS when I select “Ultra” vs “High” graphics setting.
I have RTX 3080 and guessing somehow the Ultra setting is taxing the GPU, which seems suited to handle the increase. While, the High setting is pushing the CPU more. An i9 10k I think it has a harder time with the settings. But, I feel like that’s not the story. Wonder if anyone else has noticed similar performance?
Unfortunately, I haven’t been able to conquer the CTD either way so I’m wondering if my rig is causing the problem? Have seen some great advice from the community. Hoping someone out there can assist🙏🏾