I've been seeing this issue for a while now, at least a couple of months. I don't use a screen protector, I do use auto-brightness and glance. I don't use the iris-scan to unlock, although the red LED still comes on, especially when I'm getting this black screen. I struggle to think how taking the SD card out, booting, and then replacing the SD card would affect this at all. I think the real problem must have something to do with the IRIS scan, since that's the only physical clue I have to work with - I've got it shut off, but with the black screen, I often get the red iris-scan LED.