Yes, I spotted it but then it’s always easier to pick up on these things when asked to pore over them to such a degree. It is much more difficult to exercise the same control in everything you write and we are all capable of making mistakes. Even me! “…practice writing shorter sentences.”, for example, should be “…practise writing shorter sentences.” Sorry about that! I’m also unimpressed by elevators that were ‘introduced’ to the hotel. I hope they get on very well together! Maybe ‘installed’ would be preferable. Finally - and I think this is more pertinent than the last point – in both the test sentence and your alternative, ‘top floor rooms’ and ‘lower floor rooms’ would be less clumsy. Even hyphenated. But, like a lot of these points, that is entirely subjective.