[TEAM BUILDER] Being unable to use masteries made in the same lobby

This has happened a few times to me and a few friends and here is what happens

-Want to try a new champ so we make a page for that champ -Page saves properly and is able to be selected from the drop-down menu -Select the page -Upon joining the game we would not have any masteries

This can be solved by making the page before joining the lobby or leaving and rejoining but is still rather irritating as one lapse of memory can lead to no masteries which in older season would not have made a huge difference but in S6 make the whole world