itch.io

I'm having the same issue, it seems to be duplicating any scenes placed with the tool once you save and reload the scene you've been working on.

The only thing that seems to fix it is to turn on both auto-collisions and the FBX/GLTF auto-unpack option both under the collide tab in UAP. Note that auto-collisions alone doesn't fix it and auto-unpack doesn't work without auto-collisions enabled.

Scene I'm placing:  
Placed by UAP:
 
After reloading the scene and clearing the error messages:


After making the children editable with the dupes circled: