Thanks for reaching out. Let's sort this out.
A few questions: when did the issue start? Is this only happening when casting from one app or across all apps? Are you casting a video using a mobile phone or a computer through the Chrome browser? In the meantime, try the steps listed below:
Note: If the issue persists, please reach out to your TV manufacturer for further help.
Just checking in to make sure that you've seen my response. Please let me know if you have other questions or concerns as I will be locking this in 24 hours if I won't hear back from you again. Feel free to start a new thread and we'll be happy to help.