Having problem with grand-child rotation

Hi. I am making missile trucks like MLRS.

However, there is a problem in rotating the launcher.

It is made up of body - rotation axis - launcher.

Rotation Axis is the child of the body, and Launcher is the child of the rotation axis. That is, the launcher is the grandchild of the body.

Even if the rotation axis rotates, the collision of the launcher does not rotate together.

As you can see, you can see the launcher going through the floor.

Instead, in the space where the original launcher was (ie, the empty space in the second photo), the launcher’s collision is left, so the object can not penetrate.

Why is this happening? I would appreciate your help.