So my save issue is repeatable and easily spotted, though I can't tell you why.

I have a CTD (crash to desktop) whenever I save my game, in any form (new, quick, overwrite). When it tries to save, instead of saving it under PlayerProfiles/Story, it tries to save it under Baldur's Gate 3/Temp, creating a Temp directory, then a folder under that named after the save, but the folder only ever contains the .png, not the actual save. Larian has confirmed that they can reproduce it and they are fixing it.

Where this problem shows up is after talking to a vendor...any vendor, it seems, as I've tried all of them. I have a save game where I can save and save and save without issue, but the moment I talk to a vendor, I can't save after that and it does the Temp thing above. I don't have to buy/sell, I just need to open the trade window, so I don't know precisely what's going on. I've bought/sold lots before now, but I'm at a point in my save game where the next save is a CTD after talking to any vendor in the game.