I have V16 and 1080Ti so I can check what happens with pan crop. I use Sony 4K XAVC-S media.

With four clips and adjusting pan crop all is fine and quick, been running 11-12 mins now.

same here. Works just fine.

I suspect what you're seeing has more to do with the fx you have applied in your project than pan/crop

Same here too with equipment listed in my sig.

Is it possible that after some time he gets stuck with the memory cache? 

How much ram does this system have? Enough free hard disk space for caching?

48GB RAM and 20GB free space in Hdd

Not sure that 20gb free HD space is doing you any favours.

20GB isn't much free space at all- can you free some up on the hard drive? Maybe run disk cleanup and empty the recycle bin.

I'm not sure this is your problem, though. I've never had problems with Pan/Crop myself.

I'm certain 20G free isn't causing this problem. There's something else going on.

Do you see this kind of behavior in a new project with nothing but video events on the timeline? No fx applied, nothing but going in and panning and cropping?

I'm certain 20G free isn't causing this problem. There's something else going on.

Do you see this kind of behavior in a new project with nothing but video events on the timeline? No fx applied, nothing but going in and panning and cropping?

In the new project this also happens :/

This is kind of a long shot but any chance this could be related?

https://www.vegascreativesoftware.info/us/forum/huge-problems-with-vegas-pro-18--123949/

Maybe this video will show you how it works. I have long delays and work is not possible :/

< Pan/Crop - Delay

I would start looking for problems on your system like in the link I gave above. That is definitely not typical VP behavior.

I would start looking for problems on your system like in the link I gave above. That is definitely not typical VP behavior.

I don't see anything wrong with the system

@Salah IN your screenshot it says the Nvdia Geforce RTX 2080 is being used, but in your O.P. you said this

so what must we believe that is true????

I have RTX 2080. I was wrong, but it doesn't matter.Some time ago I replaced 1080 with 2080. I want to solve a problem with vegas.

Therefore we can only help you by doing the same as you do on our installation.
You have to tell exactly what you are doing exactly.
From your YT video I could not see what you were exactly doing except that the big white screen looked like a pan/crop window with in it a very tiny picture.
Not which kind of project, what kind of file or event with a pan/crop.
So for help you need to state that exactly with the MediaInfo of the source (video?) and so on.
Maybe better is to place a veg with a short source on a site as Dropbox and provide here a link for us to download it.

It does not matter what is in the project. There may be a photo or a graphic and after a few minutes Pan/crop does not work properly. This happens when I work in 4k resolution with two monitors. After about 5 minutes I have to turn VEGAS off and on again. All other programs work correctly. 

I think you will not come to a solution with this question and answer game.
You should follow the advice of j-v if you want to come to a solution.
We are not Magix here, but a peer-to-peer forum with lots of people who would like to help others in their free time, but I would not overuse this voluntariness either.

@Salah Have you tried disabling your secondary monitor?

Also, what happened when you disabled/uninstalled the realtek driver

48GB RAM and 20GB free space in Hdd

@Salah Windows continuously copies between the two memories. This is of course a big problem for Windows, VEGAS and all other programs with a lot of cashing process. If you have 48 GB of RAM you should have at least 2 * 48GB free hard disk space (on Windows drive as reserve), otherwise the hard disk is only copying between RAM and HDD. You can check this with the Task Manager and the performance of your disk drive.