Thanks for reaching out to Roku Community.
We'd like to know more about the issue you are experiencing. To clarify, you are streaming the tv series The Mentalist through The Roku Channel. Is that correct? Have you tried to restart your Roku device and see if there's any difference? We would recommend doing this from the Settings menu by navigating to Settings > System > Power (If you do not see a Power submenu, skip to the next step.) > System restart.
Let us know what you find out so we can look into this further.