This is not a new issue but I finally remembered to actually report it.
I was just about finished with editing masteries when the game was starting. There is always a prompt about saving the edited mastery page just like when you straight up close the window. I clicked on the "Yes" button and the clicking sound is also played, but the mastery page is never saved.
Also, in blind pick mode, the game immediately enters "Pick your load out" that only lasts 10 seconds when the last person locks in the champion. First, I am sure any load out picking would require more than 10 seconds. Secondly, the game should detect if anyone has the mastery window open. If they do, it makes sense to me to not immediately enter the 10 seconds countdown because that person probably locked in the champion and is currently making edits. That person (in this case, me) will be expecting more than 10 seconds to do so but now the time is suddenly cut much shorter when the last person locks in. This is especially hard to predict when the last person to lock in is on the other team.
If these can be changed that would be great.