I have had issues with my livestream stuttering for years with no fix. I have no source dropped frames, no resyncs, no rendered drops. My CPU and GPU usage stays under 10%. My video input is always 59.94 from the camera. Ive tried changing it to 60 in vmix. Ive tried changing my monitor to 60 and 59.94 to see if it was just the monitor. Im streaming at 10,000kbps, HEVC, 1920x1080, P1 fastest, Keyframe 0.5 seconds, stream delay zero, threads 4, network buffer 20, Strict CBR checked, ffmpeg. In Performance settings resizable bar enabled, Graphics Adapter 5070 Ti, Output format UYVY, Video Rendered VMR9, Application Priority High. In Nvidia Control Panel I have Power management set to High Performance. I have also in Windows 11 right clicked on the desktop, chosen display settings, graphics, add desktop app. Added Vmix, Vmix64, ffmpeg6.exe(I cant find just ffmpeg) and selected for all of those things to use Nvidia high performance Mode. Im using an AMD 5900XT, x570 ASUS Dark Hero, Nvidia 5070 Ti, 32GB 16x2 16-19-19-39 3600Mhz Ram. Using an elgato 4KPro Mk2 pcie capture card in a pcie 4.0 x16 slot operating at x8. The card is a pcie 2.0 x4. I get the same random slight stuttering when I use NDI. Even when I use NDI bridge to reduce the video to 16Mbps. My picture quality is always amazing....but I cant stop this stutter that is very apparent on pans. Again...zero dropped frames anywhere. Even in stats for nerds on youtube. I have gone great lengths to stop this. I dont know what else to do. Im using latest version of Vmix.

Just throwing stuff in here. Don't know if it sticks. But have you tried changing keyframe interval to 1 or 2 seconds?