This has only occured in Act 3 and specifically only for the Lower City map. Playing multiplayer for the rest of the game and for outside of Baldur's gate has been smooth.

My computer is the host computer and my wife is the 'guest account'.
Loading into Lower City will occationally (more often than not) cause my wife's characters to load in T-posed, her minimap blacked out, and her character will just glide around unable to interact with anything.
If we then try to waypoint out of Lower City she'll get a black screen and my game will fail to load until her game has fully crashed out to desktop.
While this is happening there is nothing wrong going on with my computer at all.
Graphics drivers (NVIDIA) are all up to date, we've tried dropping my wifes graphic setting all to low, taken off Vsync, nothing running in the background etc etc and nothing has changed.

If we get lucky enough for it to load in normally, if we enter a cellar and then go through a door to go back to the Lower City we're gambling again and the game might T-Pose crash.
I've read around that the Lower City is causing a lot of issues for other people as well, even just in single player, so I'm hoping it's on Larians radar.
We can't really progress the story anymore because of how frequent this issue happens. Considering that everything else to this point has been crash free I have to assume there is something going on on Larians side.

Probably just typing into the wind here but really hoping Larian will look into this or someone has some idea of what I can do.
This has been game of the century for us up until this point.