So, I decided to test out an in-progress build of a land feature I'm working on, with a quick and ugly texturing job, and I noticed a bug in the terrain system. Maybe it's known about, but I couldn't find anything about it.
Basically, the game engine ignores holes in the terrain for character collision, but it seems to work okay for other items; I threw out one of the mines, and it went through the hole as it should. The model is set down into the ground, with the area inside it emptied out, as it would be in an actual scene.
I thought maybe it was an issue with my model or something during export, so I did an A/B test... one with the heightmap terrain, and one without it. Without the terrain in the scene, it works fine.
Here's a couple short vids demonstrating it...
Any idea why that might be happening?