Hi, I have been using Vegas 16 since 2018 with all types of files and never had an issue. Earlier this year I upgraded to Pro 21 and I haven't been able to use it at all.
My machine:
CPU: Intel i9 9900KF
GPU: NVIDIA 3090TI on 566.36 driver
RAM: 32gb
Windows 11 with the latest updates
All disks are NVME.
When I import a 4K MOV file taken with my Z6 II, Vegas 21 starts to act up. The preview is unusable even in draft mode. It never plays the frames and I only hear the audio. It lasts only a few seconds and then it crashes. Sometimes it even crashes the entire machine and I need to manually reboot.
If I import the same exact file in Vegas 16 that's installed on the same machine, I can edit just fine and use the preview in max quality if I want to.
I tried a solution suggested in another post to rename the so4compoundplug folder but that didn't help either because Vegas 21 won't launch after renaming the folder.
While trying many things, I got a notification from Windows asking if I was having audio issues? That seemed odd so I decided to try change the output method in the Windows settings. And Vegas 21 decided to start working properly!
So here is the thing, I am using the audio output from my 4K monitor using the NVIDIA High Definition Audio option that goes out from the card via the Display Port. This works fine with Vegas 16 btw.... Once I changed the option to the on-board Realtek output, Vegas 21 started working smoothly.
Let me know if you want more details so you replicate the issue.