I have a Hisense with a built-in Roku, same experience, but it got a lot faster once I cut off its internet access. (It's still connected to the home network so

I have a Hisense with a built-in Roku, same experience, but it got a lot faster once I cut off its internet access. (It's still connected to the home network so I can use the iOS remote control app for it, but I set up a firewall rule to block it from WAN access.) Worth a try if you can live without it dialing out.