Unable to alter rune page in champion select

After reaching the champion select at the start of a match I was unable to alter the runes in my rune page. I could only select pre-existing ones or the previously altered rune pages from previous matches. But since I went adc lucian last game with Fleet Footwork, I wasn't gonna take said runes for Sejuani, so I decided to alter them in the champion select, but unfortunately that was not possible.

This bug only happened to me once.