Second x-screen hangs in multiple-head configuration

[Evgeny S Maksimov]

On a machine with two Radeon R7 240 video adapters and four monitors (two monitors on each), when Qt 5 app actively uses OpenGL to draw the interface starts, a hanging second x-screen appears after a while. At this point, the mouse cursor over the hanging x-screen moves freely.
The problem is also typical for Kubuntu 17.04 but in the case of Kubuntu 17.10 (beta) it periodically leads to a full freezing of the X-server.

P.S.
When the DVI cable is physically disconnected from the fourth monitor the problem does not appear.
P.P.S.
The hardware of the system unit is absolutely new.

ProblemType: Bug
DistroRelease: Ubuntu 17.10
Package: xserver-xorg-video-amdgpu 1.4.0-1
ProcVersionSignature: Ubuntu 4.13.0-12.13-generic 4.13.3
Uname: Linux 4.13.0-12-generic x86_64
ApportVersion: 2.20.7-0ubuntu2
Architecture: amd64
BootLog: /dev/sda1: clean, 699983/122101760 files, 286086386/488378368 blocks
Date: Mon Oct 9 09:36:33 2017
DistUpgraded: 2017-10-05 19:03:53,942 DEBUG Running PostInstallScript: './xorg_fix_proprietary.py'
DistroCodename: artful
DistroVariant: kubuntu
GraphicsCard:
 Advanced Micro Devices, Inc. [AMD/ATI] Oland PRO [Radeon R7 240/340] [1002:6613] (prog-if 00 [VGA controller])
   Subsystem: ASUSTeK Computer Inc. Oland PRO [Radeon R7 240/340] [1043:04c5]
 Advanced Micro Devices, Inc. [AMD/ATI] Oland PRO [Radeon R7 240/340] [1002:6613] (prog-if 00 [VGA controller])
   Subsystem: ASUSTeK Computer Inc. Oland PRO [Radeon R7 240/340] [1043:04c5]
InstallationDate: Installed on 2017-09-18 (20 days ago)
InstallationMedia: Kubuntu 17.04 "Zesty Zapus" - Release amd64 (20170412)
MachineType: To be filled by O.E.M. To be filled by O.E.M.
ProcEnviron:
 TERM=xterm-256color
 PATH=(custom, no user)
 XDG_RUNTIME_DIR=<set>
 LANG=ru_RU.UTF-8
 SHELL=/bin/bash
ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-4.13.0-12-generic root=UUID=b3726d8c-94d8-41b5-b20f-e2369c18ec8c ro quiet splash vt.handoff=7
SourcePackage: xserver-xorg-video-amdgpu
UpgradeStatus: Upgraded to artful on 2017-10-05 (3 days ago)
dmi.bios.date: 06/26/2015
dmi.bios.vendor: American Megatrends Inc.
dmi.bios.version: 2603
dmi.board.asset.tag: To be filled by O.E.M.
dmi.board.name: M5A97 R2.0
dmi.board.vendor: ASUSTeK COMPUTER INC.
dmi.board.version: Rev 1.xx
dmi.chassis.asset.tag: To Be Filled By O.E.M.
dmi.chassis.type: 3
dmi.chassis.vendor: To Be Filled By O.E.M.
dmi.chassis.version: To Be Filled By O.E.M.
dmi.modalias: dmi:bvnAmericanMegatrendsInc.:bvr2603:bd06/26/2015:svnTobefilledbyO.E.M.:pnTobefilledbyO.E.M.:pvrTobefilledbyO.E.M.:rvnASUSTeKCOMPUTERINC.:rnM5A97R2.0:rvrRev1.xx:cvnToBeFilledByO.E.M.:ct3:cvrToBeFilledByO.E.M.:
dmi.product.family: To be filled by O.E.M.
dmi.product.name: To be filled by O.E.M.
dmi.product.version: To be filled by O.E.M.
dmi.sys.vendor: To be filled by O.E.M.
version.compiz: compiz N/A
version.libdrm2: libdrm2 2.4.83-1
version.libgl1-mesa-dri: libgl1-mesa-dri 17.2.2-0ubuntu1
version.libgl1-mesa-glx: libgl1-mesa-glx 17.2.2-0ubuntu1
version.xserver-xorg-core: xserver-xorg-core 2:1.19.3-1ubuntu7
version.xserver-xorg-input-evdev: xserver-xorg-input-evdev N/A
version.xserver-xorg-video-ati: xserver-xorg-video-ati 1:7.10.0-1
version.xserver-xorg-video-intel: xserver-xorg-video-intel 2:2.99.917+git20170309-0ubuntu1
version.xserver-xorg-video-nouveau: xserver-xorg-video-nouveau 1:1.0.15-2