New Vegas reproducibly crashes for me on certain modal windows with a "This application has requested the Runtime to terminate it in an unusual way" error popup.

The first instance is near the start of the game after Doc Mitchell gives you your pip-boy and a modal dialog asks you whether you want to enable hardcore mode, on selecting one of the options.

I was able to get past this crash by using New Vegas Anti Crash.

However, I get a second crash a little later on winning at caravan the third time against Ringo. NVAC logs it but is not able to prevent it. It shows an exception in KERNELBASE.dll: Now, the really weird part is that loading the same save in the Steam version of the game does not crash (Before you ask, I have both versions because I had the base game only on Steam and bought the ultimate edition on GOG).

Both versions are running on the same machine and same disk partition. I have tried
- disabling all .esms except FalloutNV.esm with Nexus Mod Manager
- copying and enabling all DLC .esms from the GOG version into the Steam one
- running with/without NVSE + NVAC, on both versions
- reinstalling the game
- verify/repair the game from GOG Galaxy
- reinstalling all MSVC runtimes

I have attached saves, screenshots and windows event log entries of the crashes.

System:
CPU: AMD Ryzen 7 3700X
GPU: AMD Radeon RX 5700 XT
RAM: 32 GB
OS: Microsoft Windows 10 Professional (x64) Build 18363.778

Edit: this forum won't let me attach a .zip, so I've uploaded it here

The problem with diagnosing this issue is that you are running the Steam edition "Vanilla" and the GoG version in "Ultimate". On top of that (and I am not sure if this is true) I have heard the GoG version contains an extra 4gb patch.

It's like comparing apples and oranges (or Red apples and Green apples).

I suggest you try running the same save with identical versions and see if the problems persists.

Try running the standalone installer with no galaxy as well, see if that works.

Given that Ultimate has extra content and modifications to the game, I am not surprised it may be less stable than the Vanilla version.

Sorry I can't be of more concrete help, but without more information there really isn't a clear cut solution that I can see.