VirtualBox does not recognize Windows 10 taskbar on the side

[chross]

I am using VirtualBox 6.1.6 on a Windows 10 host with Ubuntu 18.04.4 LTS as guest OS. I have installed the latest guest additions and am using the VMSVGA gfx driver. I am using a side-by-side dual monitor setup which is extended in Windows.

My windows taskbar is placed on the left, respectively right side for each monitor, effectively reducing the available width for maximized windows.

Since switching from 6.0.x I have the following issue: My guest OS windows will show scrollbars to view the full screen rather than scaling the viewport down to fit into the window. I am using maximized guest os windows with the "auto-resize gust display" function enabled. I have switched off the display of menu or statusbars.

When moving the windows taskbar to the bottom of my host system, all scrollbars disappear.

[chross]

scrollbars ok, taskbar at the bottom

[chross]

scrollbars ok, taskbar at the bottom

[chross]

1.jpg is actually the image where the scrollbars are not ok and the taskbar is at the left and right side of the screen