About a month ago I got a Samsung Galaxy S6 Edge bought off from Swiss carrier Sunrise. It's a 32gb model, with European region lock. My brother didn't open it in Switzerland, and he gave this to me as a gift when he arrived by airplane in Romania.
Anyway as soon as I boot the phone, I do initial setup. When I connect to a Wi-Fi network it enters a boot loop. The only way to get it back to normal is to hard factory reset it. It happened multiple times, on different Wi-Fi networks. First I did an software update with mobile data to 5.1.1 Lollipop, it didn't fix the problem. Then using the smart switch app for PC I downloaded a new original firmware, guided through live chat by a Samsung official helper, still didn't fix the boot loop issues.
Then he takes the phone back to Switzerland, where there was no problem when connected to a Wi-Fi network. He sends it to warranty for repairs, they find nothing wrong with it, after 15 days he gets it back. Just as he was about to send it back to me to Romania, he does a test and finds out that the phone entered a boot loop for the first time in Switzerland. He left the phone in a boot loop so the guys at the shop could see that the phone was definitely flawed and make sure it's going to be repaired or replaced. After another 15 days, results came back as if the phone has no problem.
They can't make it enter a boot loop so they have nothing to repair or replace, however I'm not sure what I can do. I might have just wasted 800$ and the phone is still broken