You need to do a reset on your Google Chromecast when the simple things you try do not work to fix the problems you are having with streaming. Most of the time when you have issues like the video stopping and starting or the connection dropping or the app not working right you can fix these problems by turning the Google Chromecast off and on again or by restarting your router or by closing and opening the streaming app.
You should do a reset when the Google Chromecast keeps disconnecting from the WiFi or when it does not show up in the Google Home app or when it will not complete the setup or when it freezes on the screen that comes on when you start it or when it is slow even though your internet connection is good. It is also an idea to do a hard reset if the Google
Chromecast Hard Reset was connected to a different network before and now it will not connect properly.
A hard reset makes the Google Chromecast go back, to how it was when you first got it which means it forgets the WiFi details and the accounts that are linked to it. This gets rid of all the settings so you should only do a reset when the other things you try do not work to fix the problem with your Google Chromecast.