@Wolfhard-Schurat
Test to see if there aren't any other reasons why build 452 isn't working.
For me it has been running practically without complaint, especially when it comes to crashes.
The only problem is critical media files, with extensive editing.

Have you already tried out the FAQs that deal with crash situations?
https://www.vegascreativesoftware.info/us/forum/faq-vegas-pro-won-t-start-what-can-i-do--104784/

https://www.vegascreativesoftware.info/us/forum/faq-troubleshooting-crashing-and-stability--104785/

....... apart from that, I cannot plead often enough for a controlled data backup that can be used if necessary on a functioning status.

thx for the responses. Unfortunately they do not apply to me as the previous build worked absolutely fine. I reinstalled it already. Tried all this administrator garbage only to find that if it does not work it does not work whatsoever you fiddle around.

Try resetting VEGAS Pro.

Try resetting VEGAS Pro.

Always a good idea, because the old (possibly problematic) settings are adopted when you reinstall.
When you reset, you can start with a clean installation and start with the factory settings.

after I completed the work on the veg file that crashed build 452. I deleted 421 again to go back to the latest update of Vegas 17. Hoping that the mistake was on my side. Resetted, re saved files and all the rest of it, only to find that build 452 would crash those files again, no matter what. Accompanied by the window that wants you to buy Vegas 18 ;-) lol Thx again Ian

Curious - what tools do you use to make subtitles?

A 'Titles & Text' tool?

What other Media Generator tool do you also use for that project?

Yah, sounds like a plugin incompatibility of some kind.

I'm also a heavy 17-452 user here and haven't had any problems opening files but I also have a limited set of 3rd party plugins

sounds like, could be, would be, guesswise..... guys, I respect your will to help but the problem is solved. By Ian alone, taking seriously my request to downgrade. Very simple. Pls do not try to guess the mistake on my side, for heavens sake. The project is as simple as can be. Just a video file that needed subtitles. One video track, one audio track, the titler track, no plugins. And, you could not guess it rightly. I reveal, I used........... tush, the simple titler stock plugin without any effects that comes with Vegas.

Now I tell you my guess, that might also be wrong, if Magix can prove me to be wrong. I used the animation to swap the text lines, means I did not open a new title clip for every text line. And only the videos, where I did that would not load but crash immediately. System bug, not on my side.

sounds like, could be, would be, guesswise..... guys, I respect your will to help but the problem is solved. By Ian alone, taking seriously my request to downgrade. Very simple. Pls do not try to guess the mistake on my side, for heavens sake.

@Wolfhard-Schurat
Sorry for making the mistake of trying to help you in our free time. Won't happen again.
And Vegas will probably have brought out a new update out of sheer joke and frenzy to annoy you - and not to possibly make some improvements.
https://www.vegascreativesoftware.info/de/forum/vegas-pro-17-update-5-build-452-vegas-image-vegas-effects-update-3--121144/

I don't want to deny that there can be some side effects even with further developments, which can have a negative effect in certain constellations of hard- and software, but burst in here and claim that "Build 452 is the most horrible update I ever experienced in my life", is a misrepresentation to say the least.