Entire cultures are lacking shadows on their settlement strat models. Some cultures work, some don't, and it seems that it is broken only for cultures furthest down the descr_cultures.txt file.
Looking at an earlier version the problem is not as bad: only the last culture is missing shadows. I can't pinpoint what the cause is because a lot has changed since then. The changes do include adding some extra strat models for custom settlements, if that's relevant.
It's definitely a culture problem, not a model problem. I took a model from a working culture and gave it to a broken culture: still no shadow.
It's like the game engine is running out of resources, unable to apply shadows to settlements further down the descr_cultures list.
Can anybody shed any light on this? A search came up empty.