I strongly suspect a software issue. There are reports of the same issue from all over the world from people with phones of all ages, I don;t think it could be a hardware fault for that many devices just after an update, it's too much of a coincidence.
My phone is now with the repairs crew so I can't check, I'm sure yours will be fiiiiine*.
*If it breaks send it in for repairs pronto and push it as a software issue. If they can claim it as hardware then they can push the blame on to you then you'd have to pay for repairs.
I strongly suspect a software issue. There are reports of the same issue from all over the world from people with phones of all ages, I don;t think it could be a hardware fault for that many devices just after an update, it's too much of a coincidence.