One thing I noticed about browsing the youtube homepage on PC is if your mouse hovers over a video, it starts playing, and that puts it in your watch history. So you might be accidentally adding a trash video it recommended to your watch history while looking at the other offerings. You can disable the "mouse hover auto play" by clicking your profile pic in the top right > settings > playback and performance > inline playback.

The Galaxy S5 sport had a battery door and water resistance. They just used gaskets.