Problem Solving - reservation is not in the state you think it is
Take 2 people working on the same reservation at the same time. Don't forget this is quite rare, normally good workflow would have 1 person working on 1 reservation, and another person working on a different reservation, or maintenance or admin etc.
But if its does happen, here is what happens. First of all, please refer to the diagram below:
Let's say the first person is working on Jan0001-16. They check out the reservation. Then person two comes along and loads the very same reservation Jan0001-16 into their browser. He will see it as checked out, coz that is what the server has. Lets say person 1 now checks in Jan0001-16. It will show checked-in on his screen, but not on the screen of browser 2. (don't forget this is quite rare coz normally person 2 would have done some other stuff with his BRM between the bike being checked-out and checked in)
But then lets say that person 2 decides to ALSO check in the same reservation (not knowing that he's looking at out of date information). Well, he will ask the server to do something silly, i.e. check in a reservation that is already checked-in, which would clearly be impossible. So the server responds with the message 'reservation is not in the state you think it is'. It then auto-loads your reservation within 5 seconds so that your version is up to date.
So, you see whilst you may very occasionally see this message, it is not normally something you need to worry about. If you see it a lot, talk to us and perhaps we can look at why.