It's a very common problem with a lot of causes. Most of it is the weak WiFi in the TV. Samsung support should have you put the WiFi source at 20 feet or less. It's that weak.
There's also the issue of the TV firmware. They should have you install the latest.
That's 2 items to check and the third is what WiFi channel the router is on. You want it to be from 2 to 10 for USA and 2 to 13 for other parts of the world. See the web why this differs.
I always set the DNS to 8.8.8.8 on the TV to see if that helps.
I have the new UN55KU650DFXZA and UN65KS800DFXZA and both routinely disconnect from wifi, while everything else in the house does not.
Anybody else have this problem? Help!

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