It's hard to get exact steps for this, but basically the behaviour I'm seeing is that if I leave the device disconnected, after a while (10-15 minutes, when I go to plug it back in, it is not mounted. Then no matter how many times I unplug and plug the device it will never be mounted. When I reboot it works again - for another 10-15 minutes then it breaks again in the same way.
STEPS:
1. Connect the phone via mtp ensure you can see content on both phone and sd card
2. Unplug the phone
3. Leave the phone to one side till the screen blanks
4. Now time it for 15 minutes
5. Plug the phone back in.
6. Now try and connect to the device via mtp
You now get an error message from nautilus that you can't connect to mtp, and 'ls $XDG_RUNTIME_DIR/gvfs' on the host contains nothing when it should contain the MTP device. Also on the phone 'status mtp-server' shows stopped/waiting. Restarting mtp-server and replugging, or rebooting the device revives things.
ProblemType: Bug
DistroRelease: Ubuntu RTM 14.09
Package: libmtpserver1 0.0.4+15.04.20141104~rtm-0ubuntu1
Uname: Linux 3.4.67 armv7l
ApportVersion: 2.14.7-0ubuntu8
Architecture: armhf
Date: Thu Nov 13 16:52:46 2014
InstallationDate: Installed on 2014-11-12 (0 days ago)
InstallationMedia: Ubuntu Utopic Unicorn (development branch) - armhf (20141112-181954)
SourcePackage: mtp
UpgradeStatus: No upgrade log present (probably fresh install)
I can't reproduce this on the last promoted image (#151)