Since updating to the latest software update (around 2.5gb I think - G998BXXU3BUK8) I can no longer complete all parts of the diagnostics on my phone as a part of the screen is now completely unusable and I was wondering if anyone else had experienced this or heard of the issue/solution please. (Had to rotate my phone to post this as the post button was on the part of the screen that is unusable)
Try clearing the cache partition on your phone. Sometimes that helps with post upgrade issues. Failing that you may need to do a factory reset so make sure you backup any important files from the phone first