An American film made around 1970s/80s about a haunted hotel about to be renovated.
The lift (elevator) had been stuck on the top floor since about the 1930s but voices had been heard from that floor. It is only when they get the elevator to work they discover a party of people on that floor that have been stuck in limbo for around 50 years, still wearing and doing the things they did before some sort of tragedy or disaster had struck.
This film does have a happy ending, but only when this mystery is solved by the modern hero who is to renovate the hotel.

My question to the 'Haunted hotel' query was: Does anyone know the name of this film. I forgot to ask!

It wasn't made in the 70's or 80's but Disney made a movie called Tower of Terror in the 90's at some point that sounds a lot like this. It was based of the theme park ride Twilight Zone Tower of Terror.
I'm not sure if this ride may have been based on an actual Episode of Twilight Zone or not..
Let me look some more and I'll see what I come up with.