[Client to Game Bug] Masteries Switching After New Champ Select

This happened twice today, both times playing Normal Draft with new champ select. Also both times I was playing Veigar with Greybeard skin (not sure if there is a correlation but just in case). While in the new champion select I would choose my number 11 mastery page titled 'Mage' with Thunderlord's Decree. However, once the loading screen popped up and in game it showed that I had Strength of Ages as my mastery as well as the Strength of Ages buff.

I believe that it was some how loading in one of my other mastery pages either slot 12 or slot 15 (both have strength of ages) instead of the one I selected which is 11. At first I thought it was human error, me just not selecting it properly, but then on the next game it showed my last page selected to be 11. Then when it happened again a couple of games later I figured I would report it. Hope this info helps.