Hi I have a Samsung UN58MU6100 that is only about 2 years old and having been having this issue for about a year now. It started with 2 black spots on the left side and top centre of the screen. A new one has since developed lately in the top right corner as well. Wondering if there is anything that can be done to fix this as it is very frustrating when watching something with a light background. I tried the picture test already but all 3 failed.
Please feel free to send me a private message with pictures of your symptoms that you're experiencing. As well as your full model and serial number. http://bit.ly/2tCGnGK