BoxCast not working, CheckBox overshooting

I try to procedurally build rooms, what basically works well. But as soon as I try to implement more influence by the environment (obstacles like other walls or chimneys), there appear issues.

If I try to check the room-tiles position via BoxCast to recognize obstacles, colliders are not recognized. The flat and floating wall and the chimney have primitive, non-trigger box colliders:

The script I use to cast the BoxCast:

 //Check if space is free
                     RaycastHit Hit;
 
                     if (Physics.BoxCast(NewFloorTile.transform.position, FloorTileDimension / 2, transform.up, out Hit, transform.rotation, 3f, Physics.DefaultRaycastLayers, QueryTriggerInteraction.Ignore))
                     {
                         Debug.DrawRay(NewFloorTile.transform.position, transform.up * 3f, Color.red, 2f);
 
                         print(Hit.collider.gameObject);
 
                         Destroy(NewFloorTile);
                     }
                     else
                     {
                         Debug.DrawRay(NewFloorTile.transform.position, transform.up * 3f, Color.green, 2f);
 
                         //Name
                         NewFloorTile.name = "FloorTile";
 
                         //Reference
                         Tiles.Add(NewFloorTile);
                     }

If I try the CheckBox function, obstacles are correctly recognized, but also non-existing colliders appear (the cut-out corner at the bottom with the red DrawRays):

this code is used for the CheckBox:

 if (Physics.CheckBox(NewFloorTile.transform.position + transform.up * 1.5f, new Vector3(FloorTileDimension.x / 2f, 3f, FloorTileDimension.z / 2f), transform.rotation, Physics.DefaultRaycastLayers, QueryTriggerInteraction.Ignore))
                     {
                         Debug.DrawRay(NewFloorTile.transform.position, transform.up * 3f, Color.red, 2f);
 
                         //print(Hit.collider.gameObject);
 
                         Destroy(NewFloorTile);
                     }
                     else
                     {
                         Debug.DrawRay(NewFloorTile.transform.position, transform.up * 3f, Color.green, 2f);
 
                         //Name
                         NewFloorTile.name = "FloorTile";
 
                         //Reference
                         Tiles.Add(NewFloorTile);
                     }

Any suggestions?