My camera subject switching makes it so players can see through walls???

I have a simple camera spectate script which just changes the camera subject to a parts position and then when they jump it goes back to the the characters rootpart.

The problem is when the camera comes back to the player, their camera goes through walls, like usually it collides with the walls so if they are inside of a room the camera doesn't leave the room. This glitch allows the players to see through the walls and see the whole map which isnt good.

Anyone know whats going on? or is it a glitch with roblox.

cam.CameraSubject = spectatePart

and then

cam.CameraSubject = character.HumanoidRootPart

thats the only thing i change about the camera object.. since people were asking.