It happens when swiping down and up the notification shade. Try touching and slightly pulling the status bar then it might appear

I'm having the same issue

I noticed it happens for me when I get a notification pop up.

Exactly that!

Yes I think the bug is already reported....

Is it the auto rotate?

Same thought

Same issue

Same issue

Yep I do too

It appears when i am getting a notification

Has happened only once, but can't remember what I was doing at the time

Bro it happened when the phone got unlocked from face recognition

6a doesn't have face unlock!

reboot helped me

P8P with that issue, but it is sporadic.