My Galaxy S7 phone has a black bar on the bottom of the screen that is un-moveable. Tried all different resets and things but nothing will fix it. However I put my phone on a fresh made hot water bottle for 15-20 minutes and found the heat gets rid of the black bar.... unfortunately it is only a temporary fix. It first happened in June after February update of software. If screen brightness is too high screen flickers and a larger grey box appears and covers half the screen. I think it's a problem related to the handset itself. It also happened outside of warranty. My phone is in perfect condition other than this black bar. Never been dropped or anything as I've kept it in a special bumper case to protect it. I really annoyed about it as Samsung want at least £80+ to repair it but the phone is now a few years old and not worth it. On saying that a family member was going to buy it if me for £150 and because this stupid bar has appeared I am unable to sell it which is a shame. I believe it's a fault in the phone and Samsung should be trying to resolve the issue and not charge customers money for their error.
Copy of my reply from a different thread, same issue: (note: the hot water bottle makes sense because the failure is from shrinking solder balls under the display chip; heat makes them expand, and temporarily 'fixes' the issue)
I have the same problem, S7 flat from T-Mobile. It happened a couple weeks ago. This was absolutely NOT associated with any app installs or settings changes. I use my phone a lot and was in the middle of a long text conversation when the bottom 1/5th of the screen (exactly 1/5th!) started flickering fast, then slower, slower, then black. Dead. Nothing happened to prompt this. No drops, I keep my brightness very low, phone is in a double layer case, never wet, etc.
I contacted Samsung and their response was 'screen is damage, take phone to SS to repair'. Not very confidence inspiring. I'm not paying to replace the screen when it isn't damaged. Not to mention, I don't feel I should be financially liable for component failure due to poor engineering, or because they intentionally chose cheap components that fail sooner than they should.
Interesting information: I've searched the web and found many people with this same issue with S7s, S8s, S9s, Notes, etc. Sometimes they fail vertically on one half the screen, sometimes horizontally. I came across one youtube video for a cell phone repair shop where they fixed an S7 Flat with a display problem: the screen was 'split' vertically up the middle with the left side looking fine, and the right side a sort of white static. The fix? It wasn't to replace the screen, or the logic board. Another shop had replaced the screen twice and then sent it on to this tech. The technician traced the problem to the BGA chip that controls the display. As it turns out, it is one of those chips with a bunch of solder balls under it, and due to bad assembly and/or materials, some of the solder balls lost connection. The tech removed the chip, put new solder balls on it, re-attached the chip, and that was it. Screen fixed. (this will sound somewhat familiar to anyone who had an early xbox 360 that had the red ring of death: the problem was the same. BGA solder balls that failed due to poor construction.) This is 100% NOT a problem that occurs due to any kind of misuse, from drops, apps, settings, or anything you can do to your phone short of hitting it with a sledge hammer. These problems are exclusively manufacturers defects.
I am waiting for a reply from this particular repair shop about our specific problem. I'm assuming it is the same solution but I want to be sure. I'll post a new reply when I find out for sure what the fix is, and whether it is something Samsung should be repair/replacing out of warranty for free, or if I am mistaken. I'm hoping for the former.