El Capitan media keys not responding My media keys are not working on my Mac. Pressing play doesn't open iTunes automatically. This issue occurs across all users, even newly created users, and all applications.

Here's what I've done so far:


Checked to ensure "Use all F1, F2 keys as standard functions keys" is
disabled. I've enabled and disabled this also.
I don't have chrome installed. I did, but did not use Google Play (I see this is common).
Booted into known good operating system, the keys work here.
Deleted most preference files from the system preferences that I feel could be affecting it
Copied across the rcd.app from my known good install, along with the associating launch agent
Unloaded and loaded the rcd kext from launchagent
Used safe mode and Onyx to clear all caches.
Ran fsck and used Onyx to reset file permissions
Reset ACLs for my user
Removed Plex, iControl and Adobe Premier Pro


I'm running 10.11.5 beta 4 (build 15f31a). This issue has been occurring on non-beta releases as well. I cannot think of when the issue begun, just that it's been ongoing for a few months now. I'm getting to the point where I should probably do a fresh install, but wanted to see if anyone else had any suggestions first.
The only way I could resolve this was to do a complete reinstall. I restored all data from my Time Machine backup using Migration Assistant, so I'm assuming an archive and install would work as well.