I once completed a long train journey where I tried very hard to buy a ticket and wasn't able to: website down, ticket office closed, ticket machine out of order, conductor's machine broken etc etc. I finally got the ticket from the machine outside my destination station. Before I get criticised for travelling anyway: this was back before apps and contactless, when it was more acceptable to buy your ticket on the train, before they started getting anal about it. The train itself was on time.