Hello!
I recently created my first custom content (a curtain) for The sims 3 using TSR Workshop and blender. The object is displayed just fine in the game once placed. However, the semi-transparent red "preview" of the object that usually appears when the object is placed incorrectly (i.e. in this case the curtain is hovering freely in the room or colliding with another object) is missing. The footprint is still displayed, just not the object preview itself.

From what I can tell, Blender seems to be the issue here. If I export the mesh of a cloned base game object from TSRW as a .fbx file and re-import it into TSRW without changes, the preview shows up properly in-game. However, if I export the object from TSRW, import it into Blender, then export it without change and import it in TSRW again, the preview is missing. It seems that Blender is removing some sort of property or metadata, even though I checked "include - custom properties" during import and export in blender.

Does anyone know what kind of property this might be? Or am I completely off track with my assumptions?

I am using Blender 2.93.5 and TSRW 2.0.88

I was able to solve the problem: The joint assignment was missing.
So instead of exporting from blender directly to TSR Workshop I had to import the object into milkshape, assign the joint to all vertices and then export the project from milkshape to TSR Workshop as an .wso file.