Keyboard layout changes on Shift+Shift and Alt+Alt when set to Alt+Shift

Ubuntu release: 18.04.1
Package version: x11-xkb-utils 7.7+3ubuntu0.18.04.1

Please note: I'm not 100% sure it's the correct package to file the bug against.

Since the upgrade to 18.04, I had to use gnome-tweaks to get my usual keyboard layout switching to work. It's set in options as Alt+Shift, no other option is selected (see screenshot attached), and usual Gnome shortcuts are disabled.

Expected: Alt+Shift switch the layout, and nothing else does.

Actual: Alt+Shift does change the layout, however, together with that Alt+Alt and Shift+Shift change the layout as well. This generates a lot of unwanted layout switches.

$ setxkbmap -print
xkb_keymap {
 xkb_keycodes { include "evdev+aliases(qwerty)" };
 xkb_types { include "complete" };
 xkb_compat { include "complete" };
 xkb_symbols { include "pc+us+ru:2+gb:3+inet(evdev)+group(alt_shift_toggle)" };
 xkb_geometry { include "pc(pc105)" };
};

As a workaround, Left Alt+Left Shift option works as expected, but this is still a bug.

ProblemType: Bug
DistroRelease: Ubuntu 18.04
Package: x11-xkb-utils 7.7+3ubuntu0.18.04.1
ProcVersionSignature: Ubuntu 4.15.0-34.37-generic 4.15.18
Uname: Linux 4.15.0-34-generic x86_64
NonfreeKernelModules: nvidia_modeset nvidia
.proc.driver.nvidia.gpus.0000.01.00.0: Error: [Errno 21] Is a directory: '/proc/driver/nvidia/gpus/0000:01:00.0'
.proc.driver.nvidia.registry: Binary: ""
.proc.driver.nvidia.version:
 NVRM version: NVIDIA UNIX x86_64 Kernel Module 390.48 Thu Mar 22 00:42:57 PDT 2018
 GCC version: gcc version 7.3.0 (Ubuntu 7.3.0-16ubuntu3)
.tmp.unity_support_test.0:

ApportVersion: 2.20.9-0ubuntu7.4
Architecture: amd64
CompizPlugins: No value set for `/apps/compiz-1/general/screen0/options/active_plugins'
CompositorRunning: None
CurrentDesktop: ubuntu:GNOME
Date: Fri Sep 28 13:07:55 2018
DistUpgraded: 2018-09-17 16:34:05,882 DEBUG Running PostInstallScript: './xorg_fix_proprietary.py'
DistroCodename: bionic
DistroVariant: ubuntu
DkmsStatus:
 nvidia, 390.48, 4.15.0-33-generic, x86_64: installed
 nvidia, 390.48, 4.15.0-34-generic, x86_64: installed
GraphicsCard:
 NVIDIA Corporation GM107GL [Quadro K620] [10de:13bb] (rev a2) (prog-if 00 [VGA controller])
   Subsystem: Hewlett-Packard Company GM107GL [Quadro K620] [103c:1098]
InstallationDate: Installed on 2017-12-05 (297 days ago)
InstallationMedia: Ubuntu 16.04.3 LTS "Xenial Xerus" - Release amd64 (20170801)
MachineType: HP HP Z240 Tower Workstation
ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-4.15.0-34-generic root=/dev/mapper/volgrp1-lvroot ro quiet splash vt.handoff=1
SourcePackage: x11-xkb-utils
UpgradeStatus: Upgraded to bionic on 2018-09-17 (10 days ago)
dmi.bios.date: 01/08/2018
dmi.bios.vendor: HP
dmi.bios.version: N51 Ver. 01.65
dmi.board.name: 802F
dmi.board.vendor: HP
dmi.chassis.asset.tag: CZC74688HW
dmi.chassis.type: 3
dmi.chassis.vendor: HP
dmi.modalias: dmi:bvnHP:bvrN51Ver.01.65:bd01/08/2018:svnHP:pnHPZ240TowerWorkstation:pvr:rvnHP:rn802F:rvr:cvnHP:ct3:cvr:
dmi.product.family: 103C_53335X G=D
dmi.product.name: HP Z240 Tower Workstation
dmi.sys.vendor: HP
version.compiz: compiz 1:0.9.13.1+18.04.20180302-0ubuntu1
version.libdrm2: libdrm2 2.4.91-2
version.libgl1-mesa-dri: libgl1-mesa-dri 18.0.5-0ubuntu0~18.04.1
version.libgl1-mesa-glx: libgl1-mesa-glx 18.0.5-0ubuntu0~18.04.1
version.nvidia-graphics-drivers: nvidia-graphics-drivers-* N/A
version.xserver-xorg-core: xserver-xorg-core 2:1.19.6-1ubuntu4
version.xserver-xorg-input-evdev: xserver-xorg-input-evdev 1:2.10.5-1ubuntu1
version.xserver-xorg-video-ati: xserver-xorg-video-ati 1:18.0.1-1
version.xserver-xorg-video-intel: xserver-xorg-video-intel 2:2.99.917+git20171229-1
version.xserver-xorg-video-nouveau: xserver-xorg-video-nouveau 1:1.0.15-2
xserver.bootTime: Wed Sep 26 13:36:05 2018
xserver.configfile: default
xserver.errors:

xserver.logfile: /var/log/Xorg.0.log
xserver.outputs:

xserver.version: 2:1.19.6-1ubuntu4