No Collisions inside Mesh


I recently ran into problems with collisions. I am tracking the outlines of rooms in levels of my game. This tracking is collision based. I am tracking WorldStatic and also a Custom Collision Channel.
It works as intended but i ran into some “random” trouble with some meshes and I don’t really understand the reason why.

To explain what i am doing first:
I generate a grid and do a CollisionOverlapSphere at the location of each node. The grind in the following screenshot is for debugging and visualization purposes and has no real functionality.

After tracking the collisions i track all nodes that have a neigbor which is blocked by collisions, but don’t have any collisions themselfs. With doing this only all nodes, that outline objects in the world remain.
The grey squares in the following screenshot are also for debugging and visualization purposes and don’t have any functionality.
For this i used a basic Cube provided by UE5.

When navigating into the Cube the outlines represented by the grey squares are visible:

Sofar everything works as intended and there are no problems. But when using custom meshes which are also nothing more than a simple cube i ran into problems.
On first sight everything looks fine:

But when navigating into this cube the whole problem is visible.
For this cube the outlines are tracked as intended. But also the insides of the cube also get tracked.

The explanation for this problem should be, that there are no collisions inside this cube. Therefore these boundarys also get tracked.

The collision settings of both cubes are identical.
Collisions of the cube that doesn’t work:

Collisions of the cube that works:

Can anyone explain to me why there are collisions “inside” the first cube and why there are no collisions inside the second cube? I don’t understand how this works, but it’s a major problem for my project.


Still haven’t found a solution. Can anyone help?