I was having something similar to this during early access. I use the Nvidia Studio Drivers.
Now, I can't guarantee it was one thing or the other. Maybe they patched something, but I was having those shutdowns with no crashlogs, BSOD or dumps, exclusively while playing Bannerlord (no issue with other games or software way more demanding that Bannerlord). Nvidia released a new update and I never had those crashes again (and those studio drivers always goa bit behind because they are made for reliability).
But also it could have been an issue with the Bannerlord and the RAM that possibly was patched at some point around the same time. The RAM issue was my theory all along until it stopped happening.
Anyway, somehow it got fix eventually. It's good that you have a save where you can reproduce the crash, because that certainly will tip them in the right direction. Otherwise, you just have to hope they stumble upon it.