mtpfs mounts walkman fs, but can't write to it

[Damon Smith]

Binary package hint: mtpfs

I have a sony walkman NWZ-S616F which I used to be able to write to using mtpfs. I did a format filesystem from the device itself and now when I mount the device using mtpfs it mounts ok, shows a lost+found and a Playlists folder, but any attempt to copy files into or create folders in it fails.
When I run mtpfs in debug mode I get this on start:

damon@smithd:~$ mtpfs -d usb
unique: 1, opcode: INIT (26), nodeid: 0, insize: 56
INIT: 7.9
flags=0x0000000b
max_readahead=0x00020000
PTP: Opening session
   INIT: 7.8
   flags=0x00000000
   max_readahead=0x00020000
   max_write=0x00020000
   unique: 1, error: 0 (Success), outsize: 40
unique: 2, opcode: LOOKUP (1), nodeid: 1, insize: 47
LOOKUP /.Trash
   unique: 2, error: -2 (No such file or directory), outsize: 16
unique: 3, opcode: LOOKUP (1), nodeid: 1, insize: 52
LOOKUP /.Trash-1000
   unique: 3, error: -2 (No such file or directory), outsize: 16
unique: 4, opcode: LOOKUP (1), nodeid: 1, insize: 47
LOOKUP /.Trash
   unique: 4, error: -2 (No such file or directory), outsize: 16
unique: 5, opcode: LOOKUP (1), nodeid: 1, insize: 52
LOOKUP /.Trash-1000
   unique: 5, error: -2 (No such file or directory), outsize: 16

That's without running any commands elsewhere.
If I then cd into the mounted folder in another terminal, the debug output is:
ACCESS / 01
   unique: 7, error: -38 (Function not implemented), outsize: 16

Then when I try to create a folder (in another terminal) I get:
unique: 8, opcode: LOOKUP (1), nodeid: 1, insize: 45
LOOKUP /test
   unique: 8, error: -2 (No such file or directory), outsize: 16
unique: 9, opcode: MKDIR (9), nodeid: 1, insize: 53
MKDIR /test
   unique: 9, error: -2 (No such file or directory), outsize: 16

and the command prompt returns:
mkdir: cannot create directory `test': No such file or directory

clearly this could just be my walkman malfunctioning after a filesystem format, but it still seems happy, and will play songs I transfer on manually with mtp-tools. I haven't found another box around to try it out on yet.

Using mtp-tools I can manually send files to the device and list them. Also mtp-newfolder seems to work, but then the created folders don't appear on the device folder list itself. If I try to mtp-newfolder test, then mtp-sendfile blah.mp3 test/blah.mp3, it appears to end up on the root of the walkman's filesystem.