Yes, i also googled if some other people had this issue with the phone and nothing came up.
I got the phone three days ago, today i called Samsung Customer Support; they said they'd get in contact with me but i dunno lol
Correct, the issue is present in both wi-fi and mobile data. If anything, the issue only seems to be present on YouTube. I have tried to play 1080p on other sites and i had no problem.