Comment 8 for bug 1400470

The situation got worse with 17.04 ubuntu.

The unmount trick doesn't work anymore and the camera/phone is left in strange status. I get "Can't lock camera. Unspecified error (-1)" If I unmount. I had to kill the gvfs process to be able access.

After killing
/usr/lib/gvfs/gvfsd-mtp

I got it working. but that's not the solution.