I'm not completely sure that this is a "real" problem or something about my machine (however, BGIII still runs as smooth as silk, and I'm not seeing any problems with other demanding games) - but ever since the 1.6.4 patch, I've been practically unable to play Bannerlord for the first time since early on in the development process.
The first problems were repeated Disk Write Errors to my external SSD - which I've never had before with any Steam game. It took a few different tries to clear that up, but then two consecutive validations followed by a repeated uninstall and fresh install kept leaving me with 'corrupted files' that needed to be redownloaded. I think the last one after the validation after the last clean install has left me OK, but it's acting like there's a serious memory leak again - when I open any of the windows, like garrison management in a castle or town, or trading in a village or town, the game will repeatedly freeze up for a minute or more during the process. Thumbnail images take a long time to load, and sometimes the paperdoll models will be just a head, feet, weapons and shield for over a minute while the loading catches up. Everything takes so much longer, from buying or selling supplies, to transferring troops within my army, simply because of these repeated freezes. Luckily this doesn't happen during large combats, but the game has crashed several times at the very beginning of a combat.
Up until recently, I didn't mind going back and restarting the game after a significant patch, but this game was going quite well and I was looking forward to actually moving into the later stages of clan development (children growing up, etc.). I don't actually want to sound like a whiner - I've been having a blast since I came back to it after leaving it for about 6 months, and this came as kind of a shock. I thought it was my setup at first, but nothing else I have, Steam or otherwise, seems to be having this sort of problem (yet).
The worrying thing is that it doesn't look like anybody else is struggling with this sort of thing, so I may have to scrap this game, and put Bannerlord back onto my regular HD again. Maybe it just doesn't like SSDs, or maybe my SSD doesn't like it. Anyway, this is really just a long, grumpy comment; I suspect that whatever the problem is, it's a system-related one, not a program-related one, and I'll just have to do some rearranging when I get around to it. It's a shame, because the game has really filled out nicely, and it was a real pleasure to play up until the patch. Everybody involved has done some good work!