I have exactly same issue while trying to assault Syronea, no issues with other towns or castles so far. Swap is set to 20 Gb, no success.
Summary: Game is crashing on attempting to enter a siege of Syronea. Not depends on in-game time or siege preparation actions.
How to Reproduce: Probably by trying to assault Syronea. Can provide a savegame file if needed.
Have you used cheats and if so which: No
Scene Name (if related): Syronea town
Media (Screenshots & Video):
Computer Specs:
OS: Windows 10 Home
GPU: NVIDIA GeForce RTX 3080Ti
GPU Driver Version: Latest (527.47)
CPU: AMD Ryzen 7 5800X
RAM: 32gb
Motherboard: GIGABYTE B550 AORUS ELITE V2
Storage Device (HDD/SSD): SSD