After days editing successfully all my camera and sound files on my laptop with AMD chipset I returned home and tried to continue on my desktop machine (Intel i5-10400F, 16GB RAM and nvidia quadro k1200 4GB) . Crashes ensued for 2 days until this afternoon.

I'd like to share this solution in case anyone else has the same issue - I found nothing specific online during 2 days of searching and trial and error.

e.g. when opening the existing project:    
Problem:             Unmanaged Exception (0xe06d7363)
Fault Module:        C:\WINDOWS\System32\KERNELBASE.dll

- or when dragging a file into a fresh new timeline:
   Problem:             Unmanaged Exception (0xc0000005)
   Fault Module:        C:\Program Files\VEGAS\VEGAS Pro 20.0\RegModule_x64\mx_dec_mf_audio_x64.dll

The video files were produced on my old HD Sony camcorder and the audio was 5-channel. After lots of googling and my first conversation with ChatGPT5 I suspected the issue could be Vegas and the video card not agreeing on how to process the audio.

The solution was hinted at in https://superuser.com/a/1041862/2932248 which discusses handling/converting the audio using FFMPEG.

The command line I used is this:

ffmpeg -i infile.m2ts -c:v copy -c:a aac -ac 2 outfile.mp4

This takes the contents of the original file, writes the original video stream (without changing it) to an mp4 file and then converts the 5 channel AC3 audio stream to stereo AAC format and adds that to the mp4 file. The file was recorded in a big reverberating building so I can't judge whether there is a difference in audio quality.

Vegas Pro 20 doesn't crash now on my desktop machine and I'm getting back to work.

I hope this helps someone :)