It's probably not random.

What is the media specifically you are having trouble with? https://www.vegascreativesoftware.info/us/forum/faq-how-to-post-mediainfo-and-vegas-pro-file-properties--104561/

Then what is your CPU and GPU model?

What is your version of VEGAS?

You have to provide information or we're just left guessing.

It's not specifically the media, its Vegas. I tried other projects I edited earlier before this and its the same lag/stutter after a while - the media itself is fine because I watched it in windows media player. - raw. Even when I put a raw vid in vegas it still lags/stuters eventually ONLY on the video preview, no where else is laggy.

I have an Intel i7 9700K, 32 gb of ram, Nvidia RTX 2060

I have Vegas 20

Vegas was working perfectly fine, then I moved to a new room and the preview video started to show signs of lag while editing. Making it sometimes unstable to edit - this guy I'm about to link had the same issue. His was working perfectly fine then suddenly one day the preview video started lagging: - only difference is mine is legit (i have vegas 365) and that none of his solutions work. This is my second day at this now I've wasted a solid 3hrs+ looking for any fix possible I've found ways to make it somewhat decent but its still not as before and still the video preview lags especially when I click the video preview on external monitor button so I can see my edits up close a little more than the small box on the explorer - when before this did not happen at all.

Doesn't sound like a VEGAS issue then. Open up the system and check all connections.

Do stress tests on the CPU with a tool like Intel Extreme Tuning. Try for the GPU with 3DMark (free on Steam).

If that comes up clean with performance on par with similar hardware and no overheating or crashes, then consider resetting VEGAS, sometimes updates can corrupt it.

Still have an issue? It's the media and the rest is just red herrings. How it works in a player has nothing to do with how it will work in an NLE like VEGAS.

 

It's not specifically the media, its Vegas. I tried other projects I edited earlier before this and its the same lag/stutter after a while - the media itself is fine because I watched it in windows media player. - raw. Even when I put a raw vid in vegas it still lags/stuters eventually ONLY on the video preview, no where else is laggy.

 

Vegas was working perfectly fine, then I moved to a new room and the preview video started to show signs of lag while editing. Making it sometimes unstable to edit -

@editman033 Hi, slow deterioration in performance can be due to over heating, have you put the PC where it gets less air flow or is in a warm place, maybe near a radiator/heater? As mentioned check everything is running/connected ok esp fans.

In addition to the good advice above, check in task manager that Vegas is using your GPU, click the performance tab and click the GPU tab on the left. Play the media and see if there is any activity in the video encode/decode boxes.