When I shoot a mob with a spectral arrow or give a mob a glowing effect with a command, the game (not the UI) goes black, the mob being shown as a white object in the shape of the mob. I have tested this with and without OptiFine, it happens both ways.

EDIT: The bug changes every time I launch MC. Sometimes it does what is described above, sometimes it does the same but without turnining the screen black and sometimes the effect doesn't do anything at all.