To be fair it could be that internally the system is working fine and reservations are able to be made on their side but for customers the system could be screwy.
I don't know how many times at my past job I was able to log into a customer's account and on my side everything was fine and the screens were the same screens the customer would see..but for the customer something wasn't working right. It came down to how the system was programmed for me, as an employee of the company, and how it was working for the customer. Sometimes it was also related to using Chrome, Firefox, etc that was more or less on the customer's side of things.