LibO misaligned/ghost Icon bar under certain circumstances

[Reinhard Gimbel]

While using the latest LibO apps from the libreoffice-5-2 PPA in found an inconsistency with the icon bars in the upper part of the application windows.

(1) When launching LibO-calc there is some sort of empty/ghost icon bar above the real icon bars.
(2) When creating a new file ([Ctrl]-[N]) this ghost icon bar is not available / visible anymore
(3) When re-opening a previously saved file the ghost icon bar is available / visible again

This behaviour is independed of the window mode (maximized window vs floating window) (see attachment [archive with 6 screenshots; 3x for mazimized; 3x for floating])

This behaviour seems to affect all LibO 5.2.1-rc2 apps (verified with calc, writer and impress)

lsb_release -rd emits:
Description: Ubuntu 16.04.1 LTS
Release: 16.04

apt-cache policy libreoffice-core emits:
libreoffice-core:
  Installiert: 1:5.2.1~rc2-0ubuntu1~xenial0
  Installationskandidat: 1:5.2.1~rc2-0ubuntu1~xenial0
  Versionstabelle:
 *** 1:5.2.1~rc2-0ubuntu1~xenial0 500
        500 http://ppa.launchpad.net/libreoffice/libreoffice-5-2/ubuntu xenial/main amd64 Packages
        100 /var/lib/dpkg/status
     1:5.1.4-0ubuntu1 500
        500 http://de2.archive.ubuntu.com/ubuntu xenial-updates/main amd64 Packages
        500 http://de2.archive.ubuntu.com/ubuntu xenial-security/main amd64 Packages
     1:5.1.2-0ubuntu1 500
        500 http://de2.archive.ubuntu.com/ubuntu xenial/main amd64 Packages