It happens when i want to do VFB history AB comparison - try to grab and move divider, but Max freezes for a few seconds and then disappears without a trace. Doesn't happen always, or even too often, but i had few such occasions in V11 which i don't recall to be happening in older versions at all. I don't do any rendering lately, but if it happens next time, i'll try to figure out if it's reproducible and if i can provide you with the scene to investigate.