Major graphics glitches in macOS Sierra
Since I upgraded to 10.12 Sierra on release day, I have twice experienced these major (borderline catastrophic) graphical errors on my 2015 MacBook Pro Retina. Parts of the screen go black, sometimes entire windows, the ENTIRE lock screen except for the password box, alerts such as the "Are you sure you want to restart?" window, menus come up blank, dock icons disappear, etc. Performance remains fine and programs act as if they are not blacked out, it seems to be a completely graphical issue only. See attached images. I am not sure what if anything causes this to occur, it seems completely random.
MacBook Pro, macOS Sierra (10.12), (Early 2015)