Computer Shuts Off While Editing Runes

Yep. Computer shuts off while editing runes. It’s happened three times yesterday, and once I figured out exactly how it happens, twice this morning. When I try to select something like manaflow band, my computer TURNS OFF. Riot I know this sounds crazy, but it has only happened during rune selection. Can you please fix this? I’m playing on a Mac desktop. Now I can’t even change my freaking runes at all, and if I forget in champ select about the glitch I could be facing another afk penalty out of my control. Oh yeah, and sometimes when it shuts off in champselect, IT DOESN’T DISCONNECT ME FROM THE LOBBY. So I turn my computer on to find out they remade, and I must worry about possible leaverbuster (which pisses me off.)