Spent the last 2 weeks troubleshooting a stutter that happened whenever I moved my mouse in Microsoft Flight Simulator 2020 and 2024 - whether the game was focused or not. Tried turning polling rate of my Razer mouse down to 500mhz and it improved it a little bit but it still persisted.

Worse still, when running Beyond ATC traffic injection (or AIG) my performance would cut by three quarters and stutter with crazy frametime spikes. After much troubleshooting, including reinstalling windows at least 10 different times, unplugging usb one by one, trying a different motherboard etc. finally I discovered that closing Display Fusion would eliminate the mouse stutters as well as the performance loss when traffic injection is running by one of the two apps I mentioned.

No clue why this relationship exists. I tried disabling app hook, title bar buttons etc. but no luck - only completely closing Display Fusion fixes the issue. I would prefer to keep Display Fusion running but haven't had luck with any of the compatability settings - anyone has any ideas how I could troubleshoot further?

No, that option is not enabled. The settings are mostly default