I've been the owner of a Samsung Galaxy S6 for a couple years now - in that time I've learned it's probably the worst best phone I've ever owned. I can't say I've had too many issues outside of the discoloration of a roughly 1/4 vertical slice of the screen and the battery life. The latter of the two I feel is pretty standard for a phone which peaked two versions back. Never the less, still my daily driver for the time being.
notice in the screenshot below, 95% battery - that's a full ten minutes off charge.
The other day a friend of mine dropped his S7 Edge down a flight of stairs without a case and truly believed he had wrecked his charging port. After some digging, he reported back to me that all was well and it had actually survived without issue! But... How did he know this? He used Samsung's Test Utility (the way they test devices ON the handset itself).
Pull up your phone application.
In your phone application dial:
Be greeted by the utility screen with all the options to test the hardware in your device until you isolate the issue!
Hopefully, this helps someone out there that may be having issues with their Galaxy devices and can't be bothered to ship it out for testing. Granted, you won't really be able to resolve any issues with this it's mostly just for troubleshooting to discover the actual issue THEN resolving it by other means.