Hi Megagold5,
I think the problem with the black screen after turning on the TV is not linked to the TV SW itself, but linked to an update of the app from Google, name Chromecast Android Shell app v1.18. I have had the exact same problem as you. What worked for me was uninstalling this update:
This is how I fixed it:
Press Home button on the remote and scroll down to the Settings. At the right side you will find Manage Apps. Wait for the apps to load and then scroll one row down to System apps and look for an app called Chromecast Android Shell. Check if your version is 1.1855065: this version was causing these black screens for me... If you click Uninstall Updates, then the problem will be gone. I think it's best to restart the TV by unplugging the power cord, waiting a minute and plugging it back. Let me know if this works for you