I know people have had this issue before but none of the solutions worked for me. It's always flashing unless I turn off my phone. It doesn't react to me blocking it so I don't think its actually on, just the light. I don't have Always On Display on so it's not that, and I haven't downloaded anything that's asked me for my camera or phone so I don't think it's malware or whatever.
Do you have facial recognition turned on in your settings for your lock screen or biometrics?
If you turn of facial recognition do you still experience these symptoms?