This happens all the time but i never had the time to make this thread
This is a MacOS bug that happened for quite a long time.
to reproduce the bug you have to quit back into the login menu and press the settings button and then when you go back to the menu you'll see your name a little bit glitched
And once you press the play button...oh no
This happened even before i upgraded to sierra, so pretty much happens in Yosemite - Sierra and the ones before Yosemite
The only way i did to solve this is to close the client and boot it up again, hope this gets patched soon