Have you tried removing any unused channels from your device to see if this helps improve functionality? I'd also recommend trying to remove the channel from the Roku home screen by navigating to the channel tile, pressing the * key on your remote, and choosing 'Remove channel'. Then, go to Settings>System>System restart and restart your device. Once it loads up again, try adding the channel back once more and then try playing content once more.
Let us know how it goes from there!
Roku Community Manager