When creating a new stream on YouTube, if you are presented with the 'New stream from previous' dialog, we recommend clicking the 'NEW STREAM' button.
This will take you to the default 'New stream' dialog box and allow you to configure the settings for your new stream.
If you prefer to use the 'COPY AND CREATE' button, YouTube will copy the stream settings from your selected previous stream, which could include the stream key. To ensure your new stream has a unique stream key, once you have created the stream, check that your 'Select stream key' setting is set to 'Auto-generated key'.
If you need to use managed stream keys, be sure not to use the same key for multiple streams. Multiple streams configured to use the same key will accept the same video output from STAGE TEN, effectively duplicating your broadcast.