@walter-i.: Further testing seems to indicate that the problem is not really specific to the media, or the choice of the decoder. If I remove all of the Color Grading FX from the supplied project, I do not run into the freeze problems. This seems to indicate that the slowdown caused by some of these FX results in the Engine trying to "jump ahead", and request future frames from the decoder while the previous frame requests have yet to be satisfied. This in turn causes the decoder(s) to eventually end up in a freeze state - we are looking at options to work around this. However, none of the above is 100% reproducible - while I am at times able to run the project as supplied (i.e. with the CG FX) without issues, I have not got a single freeze with the FX removed, even with runs of 2-3 hours.

Also, I made sure the computer monitors or peripherals would not go to sleep, as the brief OS/hardware activity required on wakeup seems to create more chances of a freeze (though I am not sure if this is applicable in your situation). The same holds true if VEGAS is moved to the background, and there are other applicationn/processes which take up more CPU/GPU time.

In the meantime, could you try the same experiment as me and see if you get the same results (i.e. remove all of the Color Grading FX from the video events, and run the project in a loop for a while)?

Many Thanks @VEGASHeman

I did extensive tests yesterday - and I have to say that I haven't really gotten any smarter.
While the day before yesterday I was frozen every few minutes while editing a film, yesterday I had to work very hard to freeze the system.

Here are some short notes of my tests:
Preliminary remarks:
I used the project again, which was thankfully put together by @RogerSto ensure a similar database.
- With Shuttle Pro it is possible to scroll at up to 7 times the speed.
- "JKL fast / medium / x2, 3, 4" means rewinding speed "Preferences / Edit 2-4 x keystrokes
- "Temp approx. 60 °" means average processor temperature, measured with HWInfo.

1.) without filter, loop over all events
60 min. slow run - no problems
20 min. Fast forward and backward (JKL medium) - no problems
3 min. Fast forward there and back with Shuttle Pro - Freeze.

2.) with Vegas level Cine 1 Fix blacks (input start 0.063)
20 min. slow run - no problems
10 min. Fast forward and backward (JKL medium) - no problems
2 min. Fast forward there and back with Shuttle Pro - Freeze.
3 min. Fast forward there and back with Shuttle Pro - Freeze.

3.) with Vegas level Cine 1 Fix blacks (input start 0.063) + color filter from RogerS)
20 min. slow run - no problems
20 min. Fast forward and backward (JKL medium) - no problems
15 min. Fast forward there and back (JKL fast) - no problems
10 min. Fast forward there and back (JKL Schnellx2) - no problems
4 min. Fast forward there and back (JKL fastx3) - Freeze

4.) Test with temperature monitoring processor without filter, loop over all events
5 min. slow run - no problems, temp approx. 47 ° C preview full
5 min. fast cycle (2x J) - no freezing, temp. approx. 60 ° Fan 1100, Preview full
5 min. fast run (4xJ) - no freezing, temp. approx. 70 ° fan approx. 1250, preview full
5 min. fast run (4xJ) - no freezing, temp. approx. 72 ° fan approx. 1300, optimal full

It is unusual that, especially in the last test, the system did not freeze, although I really felt sorry for the processor, and stopped the test to avoid it burning out.

In any case, I learned from my tests, that scrolling through the timeline allows processor performance to swell the fastest and highest - and should (especially with 4k material) do it more gently and slowly.

Hi Heman, that makes sense to me. While trying other Fx that tax the system (noise reduction or deflicker) I'm having crashes when done on a loop and they can't keep up.

That also explained why I got crashes after my system started throttling. Throttling (CPU limited to 700MHz) caused a performance drop and then the system couldn't keep up.

Will try playing in a loop.

[Addendum: Played the clips without any Fx at Best/Full for an hour or so. This doesn't stress the system enough to overheat and throttle, so no playback lags and no instability. I ended the test.]

Many Thanks again @RogerS for your efforts!