Sorry, messed the version up: 4.14.2 is correct

Same problem in 4.14.3.
Can I do something to support you on that? If you tell me how to debug.....

Same thing happening to my Sony Xperia c5 ultra e5506. KDE Neon simply does not recognize it.
Diferently, if I plug my smartphone to a Linux Mint, Ubuntu or even Windows it recognizes ok.

As far as I know, if the device is not recognized it means libmtp doesn't know its  vendor ID. Does this problem still happen with recent versions of libmtp?

(In reply to Elvis Angelaccio from comment #4)
> As far as I know, if the device is not recognized it means libmtp doesn't
> know its  vendor ID. Does this problem still happen with recent versions of
> libmtp?

I moved completely to Linux Mint KDE 18.3 and I can tell you it still happening. Although Mint KDE recognizes my device it freezes suddenly when I move or copy large amount of files. Usually this is the error I get: "libmtp error:  Could not get file from device."

That sounds like a different bug. So you device is recognized, right? If yes, please open another report for your issue about copying large amount of files.

(In reply to Elvis Angelaccio from comment #6)
> That sounds like a different bug. So you device is recognized, right? If
> yes, please open another report for your issue about copying large amount of
> files.

Sorry, I didn't mean that. I just tried to give you a quickly feedback. It still happens in KDE Neon and it was the reason to move to Mint KDE. Related to this one, I can - at least - connect to device although there are some issues. I don't wanna open a report for that.

I tried with 
T520:/home/docb # rpm -qa | grep libmtp
libmtp-udev-1.1.15-1.2.x86_64
libmtp9-1.1.15-1.2.x86_64

and got the following result:
Aug 18 12:30:44 T520 kernel: usb 2-1.1: new high-speed USB device number 5 using ehci-pci
Aug 18 12:30:44 T520 kernel: usb 2-1.1: New USB device found, idVendor=18d1, idProduct=4ee7, bcdDevice= 2.32
Aug 18 12:30:44 T520 kernel: usb 2-1.1: New USB device strings: Mfr=1, Product=2, SerialNumber=3
Aug 18 12:30:44 T520 kernel: usb 2-1.1: Product: Xperia Z2
Aug 18 12:30:44 T520 kernel: usb 2-1.1: Manufacturer: Sony
Aug 18 12:30:44 T520 kernel: usb 2-1.1: SerialNumber: BH90U2TV16
Aug 18 12:30:44 T520 mtp-probe[1609]: checking bus 2, device 5: "/sys/devices/pci0000:00/0000:00:1d.0/usb2/2-1/2-1.1"
Aug 18 12:30:44 T520 mtp-probe[1609]: bus: 2, device: 5 was not an MTP device
Aug 18 12:30:45 T520 kdeinit5[19139]: UdevQt: unhandled device action "bind"
Aug 18 12:30:45 T520 org_kde_powerdevil[19230]: UdevQt: unhandled device action "bind"
Aug 18 12:30:45 T520 plasmashell[19177]: UdevQt: unhandled device action "bind"
Aug 18 12:30:45 T520 baloo_file[2337]: UdevQt: unhandled device action "bind"
Aug 18 12:30:59 T520 kioexec[1433]: about to delete "/tmp/messageviewer_attachment_eIqHZN" containing "Pergamino Brisegalets.pdf"
Aug 18 12:30:59 T520 kwin_x11[19169]: qt.qpa.xcb: QXcbConnection: XCB error: 3 (BadWindow), sequence: 10240, resource id: 56623109, major code: 18 (ChangeProperty), minor code: 0
Aug 18 12:30:59 T520 kwin_x11[19169]: qt.qpa.xcb: QXcbConnection: XCB error: 3 (BadWindow), sequence: 10244, resource id: 6299846, major code: 18 (ChangeProperty), minor code: 0
Aug 18 12:31:11 T520 kwin_x11[19169]: qt.qpa.xcb: QXcbConnection: XCB error: 3 (BadWindow), sequence: 13425, resource id: 60817413, major code: 18 (ChangeProperty), minor code: 0
Aug 18 12:31:11 T520 kwin_x11[19169]: qt.qpa.xcb: QXcbConnection: XCB error: 3 (BadWindow), sequence: 13430, resource id: 6299855, major code: 18 (ChangeProperty), minor code: 0

So it identifies the Z2, but cant connect....

You'll wanna talk to the libmtp developers if this is still a problem. As Elvis said, this problem looks to be on the libmtp/mtp implementation level