Thanks for posting. Could you confirm when did the issue start? There is an issue reported earlier about the YouTube platforms, but this should be resolved by now.
If you are still experiencing the issue, could you please check if this is also happening when watching directly from the phone? Also, please reinstall the YouTube Kids app on Google TV and phone. Clearing the cache and data might also help.
Keep me posted.
Thanks for the update. Are you also getting ads when watching videos from YouTube or does this issue only occurs with the YouTube Kids app? Yes, you can sign out/in your YouTube account so we can isolate the issue. Also, if your Kid's account is logged in on the Chromecast with Google TV, please sign out/in the account.