My Galaxy Nexus 4.2.2 won't show up as a MTP device anymore. It looks like the phone is the problem, I want to debug the problem from that end.

Like many before me, I tried everything, and then some :

• Using Ubuntu 13.04 or Windows 7, on 3 computers
• Cleaning the USB port on the phone
• Using the original cables
• Reboot with or without the cable, with or without the SIM card
• Removing the battery all night (after shutting down the phone) to clear everything from memory
• Uninstalling Google Play Music (I only use MTP to sync music)

I also have a second phone that shows up as a MTP device and syncs just fine. It is also a Galaxy Nexus running 4.2.2. Neither of them are rooted. So I think the phone must be the problem.

How can I troubleshoot or debug MTP problems on the phone ?