The process of getting train tickets is semi-automatic. It still needs a human being to go to the counter at the railway station, wait in line, and buy your ticket. It can happen that in a short time, all available tickets are sold out. We show available seats until we get the information from Railways that a train is fully booked. Then we remove this departure on that day. It is a manual process, so the system can still show available seats when you get the message already that your departure is full.
The e-tickets show availability directly from the railways' system. However, it's not perfect, and the trip may actually be sold out.
If you receive an error, please try booking another train or class.