QT application is showing fallback UI

Hi,

I am new to snap packages. I tried few months ago, after facing some troubles with snapcraft i put snap packaging on my pending list. Yesterday i tried again and successfully build snap for sqlitebrowser. But now the problem is the ugly fallback interface.

Deb packages have following UI.

My snap packaging code is available on https://github.com/deepsidhu1313/sqlitebrowser-snap-nightly

Contents of my snapcraft.yaml are

      name:                   sqlitebrowser  # the name of the snap
      version:                3.10.1  # the version of the snap
      summary:                DB browser for Sqlite  # 79 char long summary
      description:            GUI editor for SQLite databases  # a longer description for the snap
      confinement:            strict  # use "strict" to enforce system access only via declared interfaces

      grade:                  stable
      icon:                   snap/sqlitebrowser.svg
      type:                   app

      apps:
        sqlitebrowser:
          # command:          wrappers/sqlitebrowser
          # desktop:          share/applications/sqlitebrowser.desktop
          command:            desktop-launch $SNAP/wrappers/sqlitebrowser
          desktop:            share/applications/sqlitebrowser.desktop
          # Correct the TMPDIR path for Chromium Framework/Electron to
          # ensure libappindicator has readable resources.
          environment:
            TMPDIR:           $XDG_RUNTIME_DIR
          plugs:
            - browser-support
            - desktop
            - gsettings
            - home
            - network
            - opengl
            - unity7
            - wayland
            - x11
            - removable-media
            - ssh-keys

      build-packages:
          - build-essential
          - g++
          - qtbase5-dev
          - qttools5-dev
          - qttools5-dev-tools
          - libsqlite3-dev
          - cmake
          - libantlr-dev
          - libsqlcipher-dev
          - libqcustomplot-dev
          - libx11-xcb1
          - libx11-xcb-dev
          - libxcb-xkb-dev
      parts:
          wrappers:
              plugin:         dump
              source:         snap/
          sqlitebrowser:      # Replace with a part name of your liking
              # Get more information about plugins by running
              # snapcraft help plugins
              # and more information about the available plugins
              # by running
              # snapcraft list-plugins plugin autotools
              source-type:    git
              plugin:         cmake
              configflags:    ["-DUSE_QT5=True", "-Dsqlcipher=1", "-Wno-dev"]
              source:         https://github.com/sqlitebrowser/sqlitebrowser.git
          desktop-qt5:
            build-packages:
            - qtbase5-dev
            - dpkg-dev
            make-parameters:
            - FLAVOR=qt5
            plugin:           make
            source:           https://github.com/ubuntu/snapcraft-desktop-helpers.git
            source-subdir:    qt
            stage-packages:
            - libxkbcommon0
            - ttf-ubuntu-font-family
            - dmz-cursor-theme
            - light-themes
            - adwaita-icon-theme
            - gnome-themes-standard
            - shared-mime-info
            - libqt5gui5
            - libgdk-pixbuf2.0-0
            - libqt5svg5
            - try:
              - appmenu-qt5
            - locales-all
            - xdg-user-dirs

          dump:               # Replace with a part name of your liking
              # Get more information about plugins by running
              # snapcraft help plugins
              # and more information about the available plugins
              # by running
              # snapcraft list-plugins plugin autotools
              plugin:         dump
              after:
              - desktop-qt5
              - sqlitebrowser
              stage-packages:
              - qtbase5-dev
              - libqt5gui5
              - libqt4gui4
              - libxkbcommon0
              - libxkbfile1
              - gtk2-engines
              - gtk2-engines-cleanice
              - gtk2-engines-moblin
              - gtk2-engines-oxygen
              - gtk2-engines-sugar
              - gtk2-engines-aurora
              - gtk2-engines-equinox
              - gtk2-engines-murrine
              - gtk2-engines-pixbuf
              - gtk2-engines-wonderland
              - gtk2-engines-blueheart
              - gtk2-engines-magicchicken
              - gtk2-engines-nodoka
              - gtk2-engines-qtcurve
              - gtk2-engines-xfce
              - gtk3-engines-breeze

              filesets:
                  wanted:
                  # - etc/*
                  # - lib/*
                  - bin/*
                  - share/icons/hicolor/256x256/apps/*
                  - share/*
                  # - usr/share/*
                  # - usr/share/doc
                  # - usr/share/man
                  # - usr/share/lintian
                  # - usr/bin/sqlitebrowser
                  # - usr/share/applications/sqlitebrowser.desktop
                  - usr/lib/*
                  - usr/lib/*-linux-gnu/*
                  # - usr/lib/*
                  - lib/*-linux-gnu/*
                  # - usr/lib/x86_64-linux-gnu/mesa/*
                  - usr/lib/*-linux-gnu/qt5/plugins/*
              prime:
              - $wanted

Is there a way to fix this ?? Am i missing something ?? I am still experimenting with snap packaging. I will be thankful for any help.

BTW when i launch app from terminal after cd to /snap/sqlitebrowser/current/bin/, UI shows as expected.

Update:
Output from terminal

  /snap/bin/sqlitebrowser 
  Gtk-Message: Failed to load module "gail"
  Gtk-Message: Failed to load module "atk-bridge"
  Qt: Session management error: None of the authentication protocols specified are supported
  QNetworkManagerInterface::QNetworkManagerInterface(QObject*) propsReply "An AppArmor policy prevents this sender from sending this message to this recipient; type=\"method_call\", sender=\":1.1549\" (uid=1000 pid=17225 comm=\"./sqlitebrowser \") interface=\"org.freedesktop.DBus.Properties\" member=\"GetAll\" error name=\"(unset)\" requested_reply=\"0\" destination=\"org.freedesktop.NetworkManager\" (uid=0 pid=1061 comm=\"/usr/sbin/NetworkManager --no-daemon \")"
  QNetworkManagerInterface::QNetworkManagerInterface(QObject*) nmReply "An AppArmor policy prevents this sender from sending this message to this recipient; type=\"method_call\", sender=\":1.1549\" (uid=1000 pid=17225 comm=\"./sqlitebrowser \") interface=\"org.freedesktop.NetworkManager\" member=\"GetDevices\" error name=\"(unset)\" requested_reply=\"0\" destination=\"org.freedesktop.NetworkManager\" (uid=0 pid=1061 comm=\"/usr/sbin/NetworkManager --no-daemon \")"
  "Object path cannot be empty"