Problem with Union and Negated wall

Hi, I have an issue with a model I made.
So I made a giant part that would be the wall. Then I made a smaller part inside to make the whole for the people to walk in. The I made a small part that is the way inside the room. But in the entrance there is some kind of invisble part that looks like you are flying, but it isnt a part.
How should I fix this?

Check the Union’s CollisionFidelity. If you want accurate collisions, you need to use PreciseConvexDecomposition. If it’s still not accurate, you should just use normal invisible parts for collisions.

If you try the Search bar up top there are quite a few posts and solutions to this problem.
Basically Unions seem to work on percentages. If you have a large part with a small percentage Negated out of it you may not even have a physical hole. If you have a 8x8 part with a 6x7 doorway in it then it’ll probably render physically perfectly fine with the MeshPart.CollisionFidelity set to Default.