I'm having this issue with my father's Galaxy Tab 4. He can be just feet from the router and even though the WiFi is strong, the internet keeps dropping on his device.
Even my crappy Dell Venue 8 almost never drops the internet despite the issues it came out with.
I already updated the Galaxy's firmware and didn't fix the issue. I found this is a documented issue in other sites but the samsungSamsung link they were giving to troubleshoot this issue was no longer working.
Any help will be greatly appreciated, thanks!