That makes sense.
After your post I tried just about every combination of any and all the various subworld settings, trying to get something partially working like yours. I couldn't get anything. So after your post clarifying to *NOT* make the collidable surface use the dynamic option, I turned that off.
I'm not sure what else I touched or what exactly happened, but somehow the collision was suddenly working. I was confused, not know what was responsible for this sorcery, so I made another platform trying to duplicate the success and see if I could figure out what caused it.
This second subworld platform was NOT working. I was completely baffled. I made sure everything was essentially the same between the two (same hierarchy relationships, on it's own prp page, all the same modifiers and settings for those modifiers).
The only difference I could see between them was their position. The first subworld platform was at the world origin. The second was naturally placed next to it.
So I thought to swap their positions. And now the first platform stopped working, and the second platform *was* working. Hmm...
I think it was the combination of having the platform exactly at the world origin (I've moved it around a bit during prior attempts to animate it), and the right settings (dynamic avatar) that got the collision working for me in the first place.
Come to discover that when moving one of these subworlds away from the world origin, the visual component of the collidable object was where it's supposed to be, but the actual collision component ends up offset.
Here is a visualization of what this offset looks like:
This is entirely in blender, not Uru. I'm not actually exporting any animations to Uru right now (one thing at a time). Just wanted to visually demonstrate what's happening.
(Besides, I still have that nagging problem where exporting an animated subworld to Uru still causes the children of that subworld to end up under the world at -2000 units (for me anyways).)
Both platforms begin the animation at the world origin. as the platform is placed farther from the origin, the collider becomes ever more distant from it.
This offset is twice the distance the subworld is away from the world origin. So I could predict where the collider would be based on where I moved the platform to.
What is also strange here is that the entry region's collision component coincides with the visual component (it's where it should be). So I needed to add an extra entry region just to get onto the offset collider.
This is the way the scene looks from Uru (looking from the opposite side, sorry, hard get everything in frame with the camera following the avatar for a shot like this).
The (very) transparent blue mesh is where the collider ends up. This blue mesh has no collision, it's only there to visualize.
blend file containing scene
At least now I can walk on to a platform in a subworld! Assuming the subworld is at the world origin and it not animated (kinda pointless). And I can't get the exit regions to work either.
Subworlds are fun...