XF86MediaPlay button doesn't work on remote but does on keyboard

Question

I have an emprex 1100 remote for controlling media, which I love. Since upgrading to 14.04 the play button on it no longer works but I can't understand why. All the other buttons work as before. A button on my keyboard with an identical keycode works fine.

I also cannot use ccsm to remap XF86AudioPlay to xdotool key XF86AudioPlay and make it work, but can remap other working keys (I am currently using "Pause" remapped to xdotool key XF86AudioPlay).

This is the xev log for the remote:

KeyPress event, serial 37, synthetic NO, window 0x4c00001,
    root 0x25c, subw 0x0, time 39090385, (1055,738), root:(2800,790),
    state 0x10, keycode 215 (keysym 0x1008ff14, XF86AudioPlay), same_screen YES,
    XKeysymToKeycode returns keycode: 172
    XLookupString gives 0 bytes: 
    XmbLookupString gives 0 bytes: 
    XFilterEvent returns: False

KeyRelease event, serial 37, synthetic NO, window 0x4c00001,
    root 0x25c, subw 0x0, time 39090497, (1055,738), root:(2800,790),
    state 0x10, keycode 215 (keysym 0x1008ff14, XF86AudioPlay), same_screen YES,
    XKeysymToKeycode returns keycode: 172
    XLookupString gives 0 bytes: 
    XFilterEvent returns: False

And this is what happens when I press the same (working) button on the keyboard

FocusOut event, serial 37, synthetic NO, window 0x4c00001,
    mode NotifyGrab, detail NotifyAncestor

FocusIn event, serial 37, synthetic NO, window 0x4c00001,
    mode NotifyUngrab, detail NotifyAncestor

KeymapNotify event, serial 37, synthetic NO, window 0x0,
    keys:  2   0   0   0   0   0   0   0   0   0   0   0   0   0   0   0   
           0   0   0   0   0   16  0   0   0   0   0   0   0   0   0   0   

KeyRelease event, serial 37, synthetic NO, window 0x4c00001,
    root 0x25c, subw 0x0, time 39091783, (1055,738), root:(2800,790),
    state 0x10, keycode 172 (keysym 0x1008ff14, XF86AudioPlay), same_screen YES,
    XLookupString gives 0 bytes: 
    XFilterEvent returns: False

This is what happens when I use a working button on the remote:

KeymapNotify event, serial 37, synthetic NO, window 0x0,
    keys:  2   0   0   0   0   0   0   0   0   0   0   0   0   0   0   0   
           0   0   0   0   0   32  0   0   0   0   0   0   0   0   0   0   

KeyRelease event, serial 37, synthetic NO, window 0x4c00001,
    root 0x25c, subw 0x0, time 39324425, (369,751), root:(2114,803),
    state 0x10, keycode 173 (keysym 0x1008ff16, XF86AudioPrev), same_screen YES,
    XLookupString gives 0 bytes: 
    XFilterEvent returns: False

Why is there a difference and how can I fix it?