The first (replacement) S8 I got had this issue. It was a FU phone.
1st S8 - black screen within 30 days.
2nd S8 - no internet (some wifi security bug in the hardware) would connect to the WiFi but could not get to the internet.
3rd S8 - 2 years now, so far so good.
Fortunately, the first 2 were so new that they replaced without too much trouble and for no charge (as one would expect).