Before December 2024 if I started a render job  of a 4 hour video to create an mp4 using the magix encoder, it would use 100% of the CPU, about 30% of the GPU, and the speed would be about 20 FPS.

Since December 2024, the same video using the same encoder on same machine uses about 20% of CPU, 20% GPU, and speed is 4FPS.

I tried suggestions on the user board and cannot figure out whether it is one of my Vegas settings, or possibly a windows update which made it slow down.

Vegas Pro 20.0  build 411.

Windows 11. version 24H2 build 26100.2894

 Dell XPS 8950 2th Gen Intel(R) Core(TM) i7-12700   2.10 GHz up to 4.5Ghz

32 Gig DDR5 Ram

 nvidia 3090 16Gig ram