Ubuntu 15.04, same thing (with HP and Trancend external USB3 hdd both). 

ubuntu@hauki:~$ uname -a
Linux hauki 3.19.0-18-generic #18-Ubuntu SMP Tue May 19 18:31:35 UTC 2015 x86_64 x86_64 x86_64 GNU/Linux
ubuntu@hauki:~$ cat /etc/os-release
NAME="Ubuntu"
VERSION="15.04 (Vivid Vervet)"
ID=ubuntu
ID_LIKE=debian
PRETTY_NAME="Ubuntu 15.04"
VERSION_ID="15.04"
HOME_URL="http://www.ubuntu.com/"
SUPPORT_URL="http://help.ubuntu.com/"
BUG_REPORT_URL="http://bugs.launchpad.net/ubuntu/"

ubuntu@hauki:~$ lspci
00:00.0 Host bridge: Intel Corporation 4th Gen Core Processor DRAM Controller (rev 06)
00:01.0 PCI bridge: Intel Corporation Xeon E3-1200 v3/4th Gen Core Processor PCI Express x16 Controller (rev 06)
00:14.0 USB controller: Intel Corporation 8 Series/C220 Series Chipset Family USB xHCI (rev 05)
00:16.0 Communication controller: Intel Corporation 8 Series/C220 Series Chipset Family MEI Controller #1 (rev 04)
00:1a.0 USB controller: Intel Corporation 8 Series/C220 Series Chipset Family USB EHCI #2 (rev 05)
00:1b.0 Audio device: Intel Corporation 8 Series/C220 Series Chipset High Definition Audio Controller (rev 05)
00:1c.0 PCI bridge: Intel Corporation 8 Series/C220 Series Chipset Family PCI Express Root Port #1 (rev d5)
00:1c.4 PCI bridge: Intel Corporation 8 Series/C220 Series Chipset Family PCI Express Root Port #5 (rev d5)
00:1d.0 USB controller: Intel Corporation 8 Series/C220 Series Chipset Family USB EHCI #1 (rev 05)
00:1f.0 ISA bridge: Intel Corporation B85 Express LPC Controller (rev 05)
00:1f.2 SATA controller: Intel Corporation 8 Series/C220 Series Chipset Family 6-port SATA Controller 1 [AHCI mode] (rev 05)
00:1f.3 SMBus: Intel Corporation 8 Series/C220 Series Chipset Family SMBus Controller (rev 05)
01:00.0 VGA compatible controller: NVIDIA Corporation GM107 [GeForce GTX 750] (rev a2)
01:00.1 Audio device: NVIDIA Corporation Device 0fbc (rev a1)
03:00.0 Ethernet controller: Realtek Semiconductor Co., Ltd. RTL8111/8168/8411 PCI Express Gigabit Ethernet Controller (rev 0c)

ubuntu@hauki:~$ lsusb
Bus 004 Device 002: ID 8087:8000 Intel Corp. 
Bus 004 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
Bus 003 Device 002: ID 8087:8008 Intel Corp. 
Bus 003 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
Bus 002 Device 019: ID 03f0:1840 Hewlett-Packard 
Bus 002 Device 001: ID 1d6b:0003 Linux Foundation 3.0 root hub
Bus 001 Device 008: ID 05e3:0745 Genesys Logic, Inc. 
Bus 001 Device 004: ID 046d:c408 Logitech, Inc. Marble Mouse (4-button)
Bus 001 Device 002: ID 04b4:6560 Cypress Semiconductor Corp. CY7C65640 USB-2.0 "TetraHub"
Bus 001 Device 005: ID 0bda:0151 Realtek Semiconductor Corp. Mass Storage Device (Multicard Reader)
Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub

/var/log/syslog when trying to eject external hdd with sidepane Eject-'button' and it pops back:

1) Nautilus/Ejecting HP (in sidepane):
May 24 19:19:47 hauki udisksd[1887]: Cleaning up mount point /media/ubuntu/HP500GB1 (device 8:129 is not mounted)
May 24 19:19:47 hauki systemd[1]: Unit media-ubuntu-HP500GB1.mount entered failed state.
May 24 19:19:47 hauki systemd[1]: Found device TOSHIBA_MQ01ABD050 HP500GB.
May 24 19:19:47 hauki ntfs-3g[9889]: Unmounting /dev/sdi1 (HP500GB)
May 24 19:19:47 hauki udisksd[1887]: Unmounted /dev/sdi1 on behalf of uid 505
May 24 19:19:47 hauki systemd[1]: Device dev-sdi1.device appeared twice with different sysfs paths /sys/devices/pci0000:00/0000:00:14.0/usb2/2-6/2-6:1.0/host23/target23:0:0/23:0:0:0/block/sdi/sdi1 and /sys/devices/pci0000:00/0000:00:14.0/usb2/2-6/2-6:1.0/host27/target27:0:0/27:0:0:0/block/sdi/sdi1

2) Nautilus/Safely Remove Drive (sidepane/secondary mouse button):
May 24 19:21:44 hauki udisksd[1887]: Successfully sent SCSI command SYNCHRONIZE CACHE to /dev/sdi
May 24 19:21:44 hauki udisksd[1887]: Successfully sent SCSI command START STOP UNIT to /dev/sdi
May 24 19:21:44 hauki kernel: [33234.367998] sd 27:0:0:0: [sdi] Synchronizing SCSI cache
May 24 19:21:44 hauki udisksd[1887]: Powered off /dev/sdi - successfully wrote to sysfs path /sys/devices/pci0000:00/0000:00:14.0/usb2/2-6/remove
May 24 19:21:44 hauki kernel: [33234.386779] usb 2-6: USB disconnect, device number 20
May 24 19:21:44 hauki kernel: [33234.773556] usb 2-6: new SuperSpeed USB device number 21 using xhci_hcd
May 24 19:21:44 hauki kernel: [33234.790061] usb 2-6: New USB device found, idVendor=03f0, idProduct=1840
May 24 19:21:44 hauki kernel: [33234.790063] usb 2-6: New USB device strings: Mfr=2, Product=3, SerialNumber=1
May 24 19:21:44 hauki kernel: [33234.790064] usb 2-6: Product: Portable HDD
May 24 19:21:44 hauki kernel: [33234.790065] usb 2-6: Manufacturer: HP
May 24 19:21:44 hauki kernel: [33234.790066] usb 2-6: SerialNumber: 000000200449
May 24 19:21:44 hauki kernel: [33234.790458] usb-storage 2-6:1.0: USB Mass Storage device detected
May 24 19:21:44 hauki kernel: [33234.790671] scsi host28: usb-storage 2-6:1.0
May 24 19:21:44 hauki logger: loading HP Device 002 021
May 24 19:21:44 hauki /hp-config_usb_printer: hp-config_usb_printer[9944]: error: This is not a valid device
May 24 19:21:45 hauki kernel: [33235.789747] scsi 28:0:0:0: Direct-Access     HP       Portable HDD     6003 PQ: 0 ANSI: 6
May 24 19:21:45 hauki kernel: [33235.790005] sd 28:0:0:0: Attached scsi generic sg9 type 0
May 24 19:21:45 hauki kernel: [33235.790160] sd 28:0:0:0: [sdi] 976773168 512-byte logical blocks: (500 GB/465 GiB)
May 24 19:21:45 hauki kernel: [33235.790386] sd 28:0:0:0: [sdi] Write Protect is off
May 24 19:21:45 hauki kernel: [33235.790388] sd 28:0:0:0: [sdi] Mode Sense: 43 00 00 00
May 24 19:21:45 hauki kernel: [33235.790653] sd 28:0:0:0: [sdi] Write cache: enabled, read cache: enabled, doesn't support DPO or FUA
May 24 19:21:47 hauki kernel: [33237.472162]  sdi: sdi1
May 24 19:21:47 hauki kernel: [33237.473294] sd 28:0:0:0: [sdi] Attached SCSI disk
May 24 19:21:47 hauki systemd[1]: Device dev-sdi1.device appeared twice with different sysfs paths /sys/devices/pci0000:00/0000:00:14.0/usb2/2-6/2-6:1.0/host23/target23:0:0/23:0:0:0/block/sdi/sdi1 and /sys/devices/pci0000:00/0000:00:14.0/usb2/2-6/2-6:1.0/host28/target28:0:0/28:0:0:0/block/sdi/sdi1
May 24 19:21:48 hauki ntfs-3g[9966]: Version 2014.2.15AR.3 integrated FUSE 28
May 24 19:21:48 hauki ntfs-3g[9966]: Mounted /dev/sdi1 (Read-Write, label "HP500GB", NTFS 3.1)
May 24 19:21:48 hauki ntfs-3g[9966]: Cmdline options: rw,nodev,nosuid,uid=505,gid=505,uhelper=udisks2
May 24 19:21:48 hauki ntfs-3g[9966]: Mount options: rw,nodev,nosuid,uhelper=udisks2,allow_other,nonempty,relatime,default_permissions,fsname=/dev/sdi1,blkdev,blksize=4096
May 24 19:21:48 hauki ntfs-3g[9966]: Global ownership and permissions enforced, configuration type 7
May 24 19:21:48 hauki systemd[1]: Device dev-sdi1.device appeared twice with different sysfs paths /sys/devices/pci0000:00/0000:00:14.0/usb2/2-6/2-6:1.0/host23/target23:0:0/23:0:0:0/block/sdi/sdi1 and /sys/devices/pci0000:00/0000:00:14.0/usb2/2-6/2-6:1.0/host28/target28:0:0/28:0:0:0/block/sdi/sdi1
May 24 19:21:48 hauki systemd[1]: Mounted /media/ubuntu/HP500GB1.
May 24 19:21:48 hauki systemd[1]: Device dev-sdi1.device appeared twice with different sysfs paths /sys/devices/pci0000:00/0000:00:14.0/usb2/2-6/2-6:1.0/host23/target23:0:0/23:0:0:0/block/sdi/sdi1 and /sys/devices/pci0000:00/0000:00:14.0/usb2/2-6/2-6:1.0/host28/target28:0:0/28:0:0:0/block/sdi/sdi1
May 24 19:21:48 hauki udisksd[1887]: Mounted /dev/sdi1 at /media/ubuntu/HP500GB1 on behalf of uid 505
May 24 19:21:48 hauki gnome-session[1729]: (nautilus:9970): Gtk-CRITICAL **: gtk_icon_theme_get_for_screen: assertion 'GDK_IS_SCREEN (screen)' failed
May 24 19:21:48 hauki gnome-session[1729]: (nautilus:9970): GLib-GObject-WARNING **: invalid (NULL) pointer instance
May 24 19:21:48 hauki gnome-session[1729]: (nautilus:9970): GLib-GObject-CRITICAL **: g_signal_connect_object: assertion 'G_TYPE_CHECK_INSTANCE (instance)' failed
May 24 19:21:48 hauki dbus[955]: [system] Activating via systemd: service name='org.freedesktop.hostname1' unit='dbus-org.freedesktop.hostname1.service'
May 24 19:21:48 hauki systemd[1]: Starting Hostname Service...
May 24 19:21:48 hauki dbus[955]: [system] Successfully activated service 'org.freedesktop.hostname1'
May 24 19:21:48 hauki systemd[1]: Started Hostname Service.