I see theres also a union called Basement. Try separating that and see if it fixes the problem! If it has, it’s because of it’s collisions.
Unions try to simplify it’s collision data when it can. If the union is big, it could make a big mistake that leaves players colliding with nothing, making them float or get blocked somehow. If you need a union to not be separated, you can set it’s collision fidelity to Precise.
It is because of the CollisionFidelity of the Union. Unless you need the Union you should separate it and make it a Model. If not try setting CollisionFidelity to PreciseConvexDecomposition.
In your case it just looks like a floor and walls so you should separate the union.
I see, so there are no walls. It is just one part with a big hole in it?
If that’s the case you can try setting CollisionFidelity to PreciseConvexDecomposition on the Union. It won’t guarantee perfect collisions but it likely will especially with square parts.
To see the collision hitboxes you can use a plugin called Mesh Optimization Tools and pressing “Show decomposition geometry”.
Your using unions for the entire building, for some reason, and thats why the collisions are all out of whack. Go to collisionfidelity and try some different settings until you find what works.
Try not to use unions, learn programs like blender!