It Is Out Of Order Too Often

The electronic book return at my local public library is a pretty cool machine. It rather feels like the machine is eating the books as it slurps them down one at a time.

However, at least half of the time when I am at the library, this machine has been “out of order.”  What percentage of the time does a machine need to be out of order before it is considered more hassle than it is worth?

I wonder if they use that sign even when they are just emptying the bin or performing some other regular but short-duration service?

On a related note, is being ‘out of order’ the same as being ‘in disorder’? Or is the ‘order universe’ large enough to contain order, disorder and still more varieties of order?