OverlpSphere returns the same Obect twice

Hello,

I wanna use a Physics.OverlapSphere to get all objects within a specific range of a center object. Everything seems to work fine but sometimes the OverlapSphere returns an object twice within the "return" list. The center object has a capsule collider and the other ojects a box collider attached. I guess it has something todo with the radius and if it hits the front side and the back side of a collider it will return the object twice.

Can someone help?