Host keystrokes to the desktop environment stop working after "Host+F" is pressed

[airmeyers]

I am running:
VirtualBox = v6.1.14r140239
Host = Windows 10.0.18363
Guest = Kubuntu 18.04.1, Linux 5.4.0-42-generic

I notice a very strange anomaly dependent on whether a host key is typed directly on the keyboard, or invoked from the VirtualBox GUI menu.

On a fresh reboot of the guest, everything appears to be working properly. All host keystrokes appear to be recognized the guest, including in the desktop environment. I test this by pressing the Super/Meta/Windows key on my keyboard, and the KDE Menu pops up just as the Windows start menu pops up on the host when this key is pressed.

- If I enter full screen mode by clicking View>Full-Screen Mode, everything is still good. The guest enters full screen mode, and keystrokes to the KDE desktop are still acknowledged (easiest test is the Super key test described above).

- Here's where it gets weird: If I enter full screen mode by pressing Right+Ctrl+F on my keyboard, keystrokes are no longer recognized by the desktop environment. Using the same example, now when I press Super, nothing happens. I have to click on the KDE menu icon for it to come up. The guest stays in this mode until I reboot.

It's not a deal breaker, but I certainly prefer to enter/exit full screen mode with keystrokes rather than GUI buttons. Any ideas?

I've attached a zipped log file for reference.

Thanks in advance,
Cole