Changing Storage Device;
Follow the instructions found here.
If that does not resolve the issue, then you will need to perform a Factory Data Reset. Make sure that the new Storage Device is connected and the old Storage Device is removed. You can find the instructions for a Factory Data Reset here.
We've completed initial testing with a number of External Hard Drives (EHD's). We've been in contact with dozens of customers that are using new EHD's and it appears that the Stream+ is more reliable when using EHD's. 1 Terabyte EHD's are very commonly used.
We do not have any specific EHD model numbers to recommend, but, we also have not heard of any EHD's that were causing any issues.