I've been doing some testing with the library backup you provided, but so far, nothing unusual has happened. In fact, I was able to load it with JRiver for Android on Android TV without a problem.
I do have a couple of questions.
Is the Shield connected via WiFi or Ethernet?Ethernet
Do you have plenty of free storage space on the Shield? After loading the library, I noticed that it's taking up 800MB of space, which has me wondering if the system is blocking it because of space limitation considering the Shields don't have much storage space to begin with.Internal shared storage is 12 GB, and I have 7.4 GB available.
For more apps, I have a 64 GB thumb drive attached and it has 57 GB available.
The 14 TB external drive has 5 TB available.
Also, regarding importing, did you try what Jim had mentioned and going into the notification, selecting the connected external hard drive and enabling 'Scan for media automatically' and then trying to import from it?Go into notification? Not sure what you mean there but in the Shield settings, the storage section has "Scan for media automatically" and yes, it was/is enabled. As for app permissions, JRiver for Android is allowed to access files and media.
I copied a lot of music files over my network to the 14 TB drive attached to my Shield. When I try to import media from it with JRiver for Android, this is what happens:
1. Navigate to Tools and over to Import and select.
2. Two options are listed, the first folder is Internal Storage, and the second is my 14 TB external drive.
3. navigate down to the external drive and using the remote hit the ring at 3 o'clock to get into the drive
4. navigate down to the Music folder and hit the ring's 3 o'clock to go into that folder
5. navigate down to an artist folder (XTC) and hit the ring's 3 o'clock to get list of albums
6. navigate to the desired album, in my case 'Apple Venus, Pt. 1' and pick the center button to select the album
7. the message "import file from /storage/thelongdrivecode/Music/XTC/'Apple Venus, Pt. 1'? and pick CONFIRM
8. an importing message appears briefly at the bottom of the screen and the import/CANCEL/CONFIRM message stays on the screen. I wait because I don't know if this means it's importing or not. At this time I cannot navigate around the screen with my remote. Eventually, the message goes away and the previous artist folder (XTC) is highlighted. I can back up to the main screen, navigate to Audio and over to Artist. Selecting Artist results in the message "View is empty."