Having this happen to me now too (6 Pro) ... Was flawless just a few days ago. Now with AOD on it appears as if the FPS is completely unresponsive until I tap to wake.
I'm also having to unlock my phone on the double press of the power button to open the camera ... Which totally defeats this shortcut LoL
Neither of these issues happen when I boot into safe mode and only appears to have surfaced a day or two ago

Haven't installed any new apps so I can't help but wonder if one of my apps updated and borked something.