Comment 8 for bug 1110483

I'm seeing this problem intermittently in Mint 18 (Mate).

dmesg shows the drive and partition are recognised
lsusb and lsblk show the partition
udevadm monitor shows the event
I can mount them manually from the command line
Same problem with flash drives and external disks

Intermittent in that it sometimes works. When it doesn't work, after about 10 minutes there's a pop up saying "time out".

I sometimes see a pop up with "operation pending".

Any clues for me?