Bottom Line: Buy a new/used One Connect Box that matches the model number of your current One Connect Box.
I own a 9000 series that went on the fritz one month ago. The picture would show up, then blue/green/red lines would fade along the screen, and finally the the whole screen would go black (with the blinking red light on the corner of the TV monitor going non-stop). This issue cycled about five more times until I never got the picture to come back on. I also experienced the same issues with remote control connectivity. I called and did the online text support -- none of the steps worked (plug into wall, default reset, firmware update, etc...). The Samsung rep pointed me to a certified repair shop, but after reading other troubleshooting posts, I saw that was not going to work.
In the process of trying to figure out what was happening, I noticed that my One Connect Box was really hot to the touch. I cracked open the case to my One Connect Box to see how it was functioning with power supplied to it. I noticed that the internal fan was no longer operational. The motherboard for the One Connect Box looked fine, but I figured that something must have burned.
A replacement One Connect Box from the Samsung site will run from $200-$475. You can probably find one on eBay for a more affordable price -- just make sure it is a match for your model number TV (just look on the bottom of your current One Connect Box; most begin with the letters "BN"). I was able to snag one for $150. Using my old One Connect Box cable, I hooked the replacement up to my TV and it worked! Picture has been solid for one month now. I'm convinced that the One Connect Box is the source of failure for most of us on this forum. It's not appealing to drop some $200 bucks for a replacement One Connect Box, but it beats buying a whole new TV system.