Yesterday, and this happened a few times as I was booking one way tickets, I would select economy fares, it would display the economy fare to purchase the ticket and then when I went to select seats it would change to first class fare and seats. Happened more than once. First time I thought i selected first instead of economy so restarted and paid close attention and the same thing happened. So tried booking the second ticket and same thing. I did eventually get my two one way flights in economy but just a weird experience of upfaring me to first automatically.

Edit: this was on the app