i think it might have a hard time with the sl avatar model + its armature?? i feel like this has happened before lol (I tried to move it to test the scale of the building again...)
I have it sometimes that my blender has issues with the rigged model, that is when I need the model only for sizing stuff I made an OBJ file of only the model and that seems to work better in those cases
Allegory: YES it worked! yay! I'm finishing a little loft house I started a while ago, since I actually bought land now I want something custom to put there! long way to go tho
but i second the unhooking avatar meshes and nuking the rest of the assoicated junk. if you don't need it, don't have it- blender can hit a memory wall and then, well, you're fucked