I had a customer call me about this issue back in February. Sure enough I got to his house and it only was showing 255 songs on his flash drive when he literally had thousands of songs stored on the drive.
Buried deep in his owners manual there was an interesting set of rules involving how to store music on your flash drive for use on your Subaru’s StarLink system.
Connectable USB storage device
Mass storage class USB memory can be connected. USB storage devices that can be played back are accompanied by the following restrictions:
Maximum directory layers: 8 layers (including the ROOT)
Maximum number of files in a folder: 255
Maximum number of folders: 512 (including the ROOT)
Maximum number of files on the device: 130,560
Maximum capacity: 16 GB or less
The issue was that the customer had was that all of his music was in one folder. Once he went back and organized his music into folders for each band and album everything played exactly as it should.
I’m sure this applies to other touch screen StarLink systems, and I’ll update this post’s tags once I come across this issue in the future.