This is the default "walkthrough" template script though--I haven't done anything to change it. If I have no script attached, it looks fine (of course, that's useless, but it still *looks* fine). So that must mean there's something wrong with the template scripts...? I'm thinking maybe there's an issue with the engine not being able to load large entities properly (and when there are many entities).

What's the main difference between "preview" mode and a default "script" mode? I mean, what kind of "template" does preview mode use to display, and why would it work?