DHS ToT has had bad, too quiet, and/or out of sync audio for years now and nothing is ever done about it. The overall lighting has been screwed around with too much and is too bright in the boiler room. There are several lighting effects missing from the drop sequences.
In the corridor scenes (the first scene), the image of the "ghosts" is also projected into the floor and the screen for the floating window at the rear of the scene is now obviously a screen, unlike when it opened. Just to name a few things.
The ride has never ever gone down for a refurbishment (occasionally one side will close for a few days at most) and it really, really needs it
It's such a draw that they have no real desire to close both sides of the ride at once. They could do an invasive refurb on each side without a full downtime of the building, but they don't even want to spend the money on that. It's sad.