What model of Roku are you using and what version of the OS? If it is an old Roku Device or one with an older OS, that might explain the reason you are having issues with the app because an older device or older OS might not be able to handle the latest Netflix app updates.
If that is not the case, it is possible it is an app issue, Roku does not control how those apps are programmed unless they own the channels themselves, although I have not seen any Netflix issue with the Ultra I have.
I know you said you have done some of the troubleshooting steps, but I suggest Uninstalling the app, then restarting or even unplugging the Roku device for 30 to 60 seconds and then reinstalling the app again.
