I have a 75" MU6300. I don't use any built in apps for this TV, simply running all media from 1 of the HDMI ports and external devices. Every now and then in the last month or so, sporadically, the native built in TV app takes over the screen and wants me to sign in. If I find my OEM controller and hit exit, it returns to the HDMI in use. (I can't delete this app, but I don't want to use it)
I tried everything but I can't seem to find a good reason it pops up? Does the TV think its going into screensaver mode or similar? Any ideas?
I was having all the same issues you are having and more with my 2017 UHD Smart TV UN50MU6300FXZA. I had great customer service with this number 800-726-7864. Basically I needed to upgrade to the newest firmware version: 1299.210623 but I couldn't because my tv would not connect to the internet via wifi or ethernet. so I downloaded the newest firmware to my pc: XXXXX unzipped the file to my pc and only moved the 2 files to and empty usb (.txt and .msd)
here are the instructions that were emailed to me:
Please follow the instructions below : 1. Click the link to download the software for your TV : XXXXX 2. unzip the file , Right click on the file and select “EXTRACT ALL....” or “EXTRACT HERE” This will save an unzipped folder with the same name. Inside of the unzipped folder, there will be 3 folders. Copy all 3 folders onto the root of a USB thumb drive that has at least 8Gb of free space. (This means to put them directly on the USB without putting them into a folder on the USB 3.If done correctly, you should have these 3 files on your USB drive. Not placed in any other folder. Steps to follow on your TV : 1. Make sure the TV is off, and attach the USB drive to the USB port on the back of the TV. 2.Turn the TV ON and press the SETTINGS button on the remote control. 3. Navigate down to SUPPORT, and then to SOFTWARE UPDATE 4. Select UPDATE NOW. And then press ENTER 5. A message to search for USB update files will appear. Press enter on YES 6.The Software Update will start automatically. 7.When complete you will be notified and the TV will turn off and on automatically. To complete the update, press and hold the POWER button on the remote for 6 seconds. The TV will restart and you will see the logo appear on the screen. Thank you.