I too have just recently noticed this issue with my MU7000 and the band is becoming more and more prevalent as time goes on. This issue is an extremely common issue just based on the posts in the Samsung community forums and most posts regarding this issue have photos posted showing the issue.
Thank you @SamsungMod23 for your suggestion to preform the Picture test. I completed the picture test on my television and it failed all three tests.
I have attached a photo of the Picture Test results:
I just noticed that there appears to be a second dark verticle band appearing as is clearly visible in the picture of the Picture Test Result screen.
As it is clearly a rampant issue with Samsung TVs and seems to span the entire model line of TVs; 6 series all the way up to QLED models.
I would greatly appreciate it if someone would address this issue with my TV, as I am extremely frustrated and disappointed that this TV, which is less than 2 years old has such an acute defect, which appears to be getting worse as time progresses.
@usermP8DT0Om8i I am sorry to about this! Here are some troubleshooting steps you can try: http://www.samsung.com/us/support/troubleshooting/TSG01202526/ If you are still seeing the spots, please send a private message with the full model code and serial number so I may look into repair options: http://bit.ly/2XERsky