This links you to the music transfer notes I mentioned previously. Not certain if there are differences by HAP version but should be enough to get you going in the right direction.
HD Failing on Sony HAP-Z1ES HDD Player, Need help from Owners of Sony Player
The hard drive in my Sony HAPZ1ES HDD player seems to be failing. After playing for a while, the player starts to skip and go back to the beginning of the song. Once this happens, every file on the player will do it. If I shut off for 5 minutes, it will work fine again for a while. I have concluded that the 1TB Hard drive is failing.
I want to replace the drive with either a 1 or 2 TB SSD. My question is how do I get the Linux software which runs the player onto the new Hard drive? I know a few members have done just that. I am hoping they can advise me. I won't have a problem copying the hd contents, just worrying about getting the operating software onto the new drive. When I look into the HD on the player, I am not seeing the software.