And when opening 2 instances of V22, it's instant armageddon. 

This might suggest that Vegas Pro 22 is the problem (assuming that Vegas Pro 21 is not also open at the same time). In my experience, there shouldn't be a problem with having 2 instances of VP22 open at the same time or any other VP version for that matter.

I wonder if resetting VP22 back to its default (factory) settings might help. Resetting is a simple straightforward process outlined here:

https://www.vegascreativesoftware.info/us/forum/faq-how-can-i-reset-vegas-pro-to-default-settings--104646/

The downside that any and all custom settings will need to be reset.

@Mindmatter I think you might have encountered the same problem as mine: https://www.vegascreativesoftware.info/us/forum/problem-to-open-more-instances-of-vegas-pro-22--148817/

not sure it's related to the general issues i have in this particular project ( reported here ), but I ported the project back to V22 from 21 for workflow reasons, and still get heavy crashes like once per hour with different crash reports each time, but mostly related to OFX and GPU stuff.

I don't see any reason to export/import a Vegas22 project back to Vegas21. When there're issues in the VP22 project, then I would try to solve the issue(s) in VP22. As you described in the linked other thread, there seem to be a render crash at a specific point in your project, for that issue I would try first to render that specific point/region with the "render to new track option" and see if it works that way, when yes, leave that new videotrack in your project (just mute the generated audio track) and then render the whole project.

not sure it's related to the general issues i have in this particular project ( reported here ), but I ported the project back to V22 from 21 for workflow reasons, and still get heavy crashes like once per hour with different crash reports each time, but mostly related to OFX and GPU stuff.

I don't see any reason to export/import a Vegas22 project back to Vegas21. When there're issues in the VP22 project, then I would try to solve the issue(s) in VP22. As you described in the linked other thread, there seem to be a render crash at a specific point in your project, for that issue I would try first to render that specific point/region with the "render to new track option" and see if it works that way, when yes, leave that new videotrack in your project (just mute the generated audio track) and then render the whole project.

As I mentioned, I‘ve tried and applied every workaround known to man kind in V 22… the crashes are not only in rendering but I regularly get total Windows crashes just working in V22. i can live with those, as I habitually save like every 15 seconds and they occur roughly once per hour. i still prefer 22 to 21 though.

I agree I‘ll have to try and prerender certain sequences if I can‘t find another solution to the V22 render issue. Maybe I‘ll eventually stumble upon the reason of the problem.

And when opening 2 instances of V22, it's instant armageddon. 

This might suggest that Vegas Pro 22 is the problem (assuming that Vegas Pro 21 is not also open at the same time). In my experience, there shouldn't be a problem with having 2 instances of VP22 open at the same time or any other VP version for that matter.

I wonder if resetting VP22 back to its default (factory) settings might help. Resetting is a simple straightforward process outlined here:

https://www.vegascreativesoftware.info/us/forum/faq-how-can-i-reset-vegas-pro-to-default-settings--104646/

The downside that any and all custom settings will need to be reset.

Thanks, I did do a reset, it did not help. I usually have 2 instances open at the same time without any issue also different versions, and I still don‘t understand what the current problem is.

Can't say I've ever experienced this. Here is a screenshot of one VP21, and two VP22 projects open at the same time.

I do have in Preferences to close media files when VP isn't the active app.

Thanks I will try changing that setting as I usually leave media online so Vegas reopens faster when coming back to it fron another running program like Photoshop etc.