Hello there DZDZDZ,
There is a issue with select systems where alt-tabbing while in full-screen mode can cause unexpected freezes. Based on responses I have seen in the Technical Support forum, Blizzard is aware of these issues though its not affecting a majority of our community.
I recommend one of the two workarounds to avoid having this happen.
- Avoid Alt-Tabbing your game while in full screen mode. I personally use my mobile device to do light browsing when I am in a queue for a game (that or I am practicing my shots in a skirmish).
- Switch to borderless window mode in your video options. When in this mode, your graphics card is keeping the display output to the native Windows Desktop resolution, so there is no freezing when trying to switch to the game’s native output. Unfortunately this setting may result in loss of performance including frames-per-second on some systems.
Please note, regardless of technical malfunction, penalties caused by leaving games in Competitive Matches cannot be reversed. To learn more about this policy, please see this topic for details: