Terrain layer suddenly missing in builds, unchecking Draw Instanced fixes it

I’ve been working on a new project for a few weeks. Been using MapMagic2 for the terrain, which doesn’t appear to be related as it doesn’t manage rendering, just generation. In past builds, my single terrain layer using a single texture for testing purposes was rendering fine.

Now I’ve noticed that in builds, it’s not rendering. The terrain is there - I can move my player and it responds to terrain. I’m not sure at which point it broke.

Based on other topics I noticed that unchecking Draw Instanced solved it - but I had never had that unchecked before. Everything works fine in play mode - it’s only breaking in windows builds.