I have this problem even with the TBM 930. After around 4+ hours it starts to lower the fps and the sound starts crackling and nothing helps to fix it … GPU and cpu are around 55C, RAm Usage is always between 50 and 63% - i tried all switching ai, wheater etc… off - nothing helps 5600x, 1080TI, 32GB …
It’s the top menu option, with the pilot cap icon. When you access it and there’s a airport, POI or a city nearby you can set this is a destination. I just set this destination and cancel. Like magic the FPS come back to the normal.
Unfortunately sometimes I’m not in computer when the fps drops and I got CTD before could save it.
The downside of this is that you have to be nearby some destination. That’s a annoying for the one that like long hauls.
so guys after a bit of experementing i found that setting a destination for the atc ai helps a little bit ( i in am SU9 Beta ) for my oppionion i get the degredation regardless of moving or not but i noticed the following: if u have lots of trafic going inside your home network like QOS appications ( Audio protocolls over network, NDI Video streams, or even a youtube or twitch livestream) The sim will Stutter much more frequently and the fps degradation happens even faster. when it so happens that have just like me multiple Network interface Wifi Lan Virtualbox lans VPNs Bluetooth. the degradation happens even faster. And data flowing in and out of the sim ( Like our beloved FBW 320x) increase at least the speed of degredation even more
MSFS Installed on a Sata SSD
I had the same main thread problem. In the meantime I have been able to fix it. The culprit was the FSUIPC7. This was detected as a virus by Microsoft Defender. Also the Xbox toolbar played a role. My steps were:
I deactivated the xbox toolbar in the Windows settings.
I removed the FSUIPC7.exe from the virus scan, as well as the FSUIPC7.bat file. since then the MSFS2020 runs as usual without performance drops over time.
Removed add-ons that I wasn’t using (an airbus chopper and YourControls)
Added FSUIPC.exe MSFS.bat and the entire FSUIPC folder on WindowsAntiVirus exceptions
Turned off X-BOX Game Bar
I will now be running the FlyByWire A320 Experimental versioning attached (FYI, never had issues prior to 3 days ago, was on FBW dev which didn’t have any updates at the time and have issues with vanilla aircraft too)
I already see a improvement if you can call that even, the FPS counter is now green, not red.