I've finally gotten to the final boss fight in the Blood and Wine expansion. In the third phase of the fight where Geralt has to kill all 3 of his hearts, the game crashes to desktop with no indication of an issue or an error message. I've not had any of the issues with the Next-Gen update that some have had. I found several posts on the Steam forum about the same issue - only in the third phase of the fight. Have I been playing for two months only to have my experience ruined by not being able to finish the game?

Happens to me, too.

Like clockwork during the third phase of the fight and most frustratingly it happeend twice during the video segment after I beat the boss.

This is incredibly frustrating and ruining my entire playthrough experience.

Im Lucky, killed Detlaff today flawless with GasHeft sword found below CloudsCastle and finished BloodWine with the good end. PC 4.02 FSR2 max 60 fps limit, no mods i7 haswell 1660ti win10, 4.01 wass much less stable for me.

Everyone who having problems with game crashing (nvm if it's DX11 or DX12) should fist do:
1) delete all "dx12user.settings" and "user.settings" file in ur "<documents>/The Witcher 3" Folder. (When you start the game this files will be automaticly restored to default config, you just need to configure again ur in game gameplay, graphic, video etc. settings)
2) go to "<ur game directory>/bin/" folder and delete folders: "x64_dx12" and "x64" and "config" (if u having mods ini files there, then first do backup of thoes) and run game werify/repair in GOG/Steam client, to downloads thoes files again.
3) delete "Mods" folder if you have it in "<ur game direcotry>/" (first do copy of ur mods if you have ones)
4) update ur GPU drivers and Game update to newest version.
5) go to "<ur game directory>/bin/x64" (for dx11) or "... bin/x64_dx12/" and open properties of ur file: "witcher3.exe", go to tab "compatibility" and mark "run this program as an administrator" and also "disable fulscreen optimizations". Remember to first run game witchout any mods installed!
6) disable all in game overlay, on Steam settings, GOG settings, on Geforce Experiences Settings or AMD Adrenaline.
7) if you playing on laptop, then change ur system power plan to "Performance" and in your dedicated GPU Control Panel change 3D program settings for your game exe and then select preferred graphic processor for this program/game to "High performance <ur GPU> processor"
8) if still DX11 mode crashing and if ur GPU supports Vulkan technology, then download DXVK dll:
- download newest "dxvk-...tar.gz" from: https://github.com/doitsujin/dxvk/releases
- unpack this file and from "x64" folder copy: "d3d11.dll" and "dxgi.dll" in to the same location where is the game .exe (This will force the game to use vulkan instead of the DX11)
9) for AMD RX 7900 XT/X series GPU try to change game AA from FSR to TAAU. (Yea i know u will get smaller performance, but for now it maybe only available solution, untill AMD or CDPR fix it in new driver/game patch, that lost performance in RT you can restore by installing my mod: All-In-One RT Tweaks
10) if you ur PC have lower then 32GB RAM, then Increese system virtual memory size:
Click Start > All Programs > Control Panel > System > Advanced > Performance > Settings > Advanced > Virtual Memory. Click Change. In Customize size set "Initial Size" to 16384 (MB) and "Maximum Size" to 49152 (MB) (or 65536 MB max)
11) If ur game crashing at same specific place or quest cutsceen then change to other DX mode (DX11 or DX12) and complite this quest or do more progress and then save and return back to previous DX mode