Not the same exact problem, but on both of my TVs, I get very good reception, but very choppy sound once in a while. When this occurs, both TVs are choppy, not just one. I have to reboot the router, and so far, the problem goes away. Yours being a 4K TV, make sure your bandwidth is appropriate.
My rebooting process is that I have to disconnect (pull) the router power cable for about 5 minutes; I have no power button. The 5 minute pause gives me a totally new circuit connection with my ISP and not the same connection if I do a quick reboot (I've checked this in my router.). Give it a try....????