Game crashing bug

I dont know if this happens to everyone, but my game sometimes after alt+tab gets blackscreen and doesnt allow me to close the game itself and join again the game. Even after restarting the pc it keeps being bugged. Its not the first time, it happened to me lik 5 times in the last month, making me loose ranked games. This really sucks and cant keep being like this. Pls fix ur game and euw server. Pd: the problem is not my computer, it is valued in 2000 euros.