This is happening to me now, i will tell you how they have made this client, they have a billion of monkeys randomly pressing keys until the program compiles then they cover up the mess with some ux.
Getting penalized for a problem that THEY have created it is just ridiculous.
They gonna fix this problem when someone on reddit hit the first page, when and employee have his game ruined by this bug, when a pro player will have this issue on stage.
If any of the above have just happened well, they are incompetents and we must deal with that...
They have announced a new client tho, this will fix all the problems by creating new problems so that we are gonna to forget this problems.
BTW i have notice that closing the browser fix the problem, i believe browser and lol client share the same vram.