Thanks. Here is my system info: Pc Dell XPS8930 (x64-based PC); Windows 10 Home (version 10.0.17134 Build 17134); Memory (RAM): 32.0 GB; Intel(R) Core(TM) i7-8700K CPU @ 3.70GHz, 3696 Mhz, 6 Cores, 12 Logical Processors;

Also: Vegas Pro 15.0, Build 416

And what's the MediaInfo of your sourcefootage
Maybe it is possible to upload a short file of that source to a cloud service like Dropbox that we can try.

In the meantime try to update your Graphic drivers of your Intel GPU included in your i7processor.

Graphic driver updated already as part of the many attempts to fix the problem. Here is a .veg file info, as requested: General
Complete name                            : G:\Vegas projects 2015 and beyond\Italian trip Sep-Oct 2018 - TUTTO.veg
File size                                : 4.69 MiB
 

And another AVI file previously prepared:

Complete name                            : G:\Vegas projects 2015 and beyond\Italia-Mexico Novembre 2016 video for windows HD 1080-24p YUV.avi
Format                                   : AVI
Format/Info                              : Audio Video Interleave
File size                                : 444 MiB
Duration                                 : 4 s 671 ms
Overall bit rate                         : 797 Mb/s
TCOD                                     : 7452027916
TCDO                                     : 7498741249

Video
ID                                       : 0
Format                                   : YUV
Codec ID                                 : UYVY
Codec ID/Info                            : Uncompressed 16bpp. YUV 4:2:2 (Y sample at every pixel, U and V sampled at every second pixel horizontally on each line). A macropixel contains 2 pixels in 1 u_int32.
Duration                                 : 4 s 671 ms
Bit rate                                 : 796 Mb/s
Width                                    : 1 920 pixels
Height                                   : 1 080 pixels
Display aspect ratio                     : 16:9
Frame rate                               : 23.976 (24000/1001) FPS
Color space                              : YUV
Chroma subsampling                       : 4:2:2
Compression mode                         : Lossless
Bits/(Pixel*Frame)                       : 16.001
Stream size                              : 443 MiB (100%)

Audio
ID                                       : 1
Format                                   : PCM
Format settings                          : Little / Signed
Codec ID                                 : 1
Duration                                 : 4 s 671 ms
Bit rate mode                            : Constant
Bit rate                                 : 1 536 kb/s
Channel(s)                               : 2 channels
Sampling rate                            : 48.0 kHz
Bit depth                                : 16 bits
Stream size                              : 876 KiB (0%)
Alignment                                : Aligned on interleaves
Interleave, duration                     : 246  ms (5.89 video frames)
Interleave, preload duration             : 250  ms

Thanks. Here is my system info: Pc Dell XPS8930 (x64-based PC); Windows 10 Home (version 10.0.17134 Build 17134); Memory (RAM): 32.0 GB; Intel(R) Core(TM) i7-8700K CPU @ 3.70GHz, 3696 Mhz, 6 Cores, 12 Logical Processors;

Do you also have a dedicated GPU in your system?

A have of course a GPU. What do you mean by "dedicated"? And, in any case, why would Vegas Pro work flawlessly for many months with the system, and then all of a sudden crash every single time?

A dedicated GPU is graphics help other than an integrated Intel GPU, something as a Nvidia graphics card.
I tried the kind of files that crashes your PC and they play without any problem with me with both disabled Graphic processors I have.
I think something happened to your computer, maybe you can reset it to a date all was working well. Other cause I cannot image with the little knowing I have. Sorry I 'm not able to help you further.

If my Vegas was working fine and suddenly started to do strange things, I would first do a full reset.....while holding down 'Shift+Ctrl' keys double left click on the Vegas pro desktop icon, check the box to 'Delete all cached application data' then click on 'Yes'

If that didn't fix it I would be suspicious the Windows 10 updated the graphics driver and Vegas doesn't like it, so I would try rolling back to an earlier driver version.

When we post a problem and ask others to help, we know what we see and have done, but they do not. Sometimes other users ask questions which may seem odd or redundant, but it is there way I trying to get information that may be helpful for them to help us. I've found the best method is to furnish up what they ask in hopes that it will lead to a solution, after all it is us asking them to spend their time to provide a solution. Just my thoughts, your mileage may vary!

Yes of course! I didn't mean to be cut and dry to anyone: if that's how it sounded, my apologies. I actually appreciate immensely everyone's comments! I'll try resetting to a previous version and will keep you posted.

Maybe try resetting your current version first as suggested by Eagle Six?

Uncompressed YUV is a bit different, and not a format that Vegas can output.

How was the footage created?

Could you possible share a short sample file on a cloud service (e.g. Dropbox, Google Drive, OneDrive, mega.nz, wetransfer.com or mediafire.com) for users here to test on their systems, and to link the developers to?

A have of course a GPU. What do you mean by "dedicated"? And, in any case, why would Vegas Pro work flawlessly for many months with the system, and then all of a sudden crash every single time?

You didn’t list the graphic card in your specs and you also didn’t mention which driver you updated to the latest.

Don't forget the Vegas' native Sony YUV renderer which outputs both 8 bit and 10 bit uncompressed YUV (better known as V210). I think this is what was done by Stefano, at least the Sony YUV renderer outputs files with same properties as the one Stefano shown above.

But I don't know what could Vegas Pro cause to crash when reimporting its own Sony YUV file.

@Marco. Thank you. I never realised that Sony YUV was "uncompressed". I thought it was doing some compression.