Old Issue is Back: Erratic mouse and/or Guest applications windows not working

[kvbuser]

This is a new post but exhibits similar problems as in this post from mid-2016, "Erratic Mouse Behaviour after v5.0.18 upgrade". My workaround back in 2016 was to revert to Vbox v5.0.16 r105871. That worked. At that time my PC was:
Vizio CN15-A5
mem: 16GB
Proc: Intel Core i7-3610QM cpu @2.3HGz x 8
Graphics: Intel Ivybridge Mobile

About a month ago I had to replace my laptop. The new system is:
Host: Ubuntu 16.04 64bit
Guest: Win10Pro 64bit
Platform: Dell XPS 15 9055

I'm experiencing problems on Win10Pro Guest where randomly I can no longer move windows around. E.g. MS office applications windows cannot be resized or moved around on the desktop. The left and right mouse buttons still seem to work but i.e. in MS Office I can access the drop menus and make selections, right click context menus are still accessible. The behavior varies with applications. E.g in SolidWorks (a CAD program), when I left mouse click on the appplication main menu e.g. File, the menu briefly appears and then rolls back up, before I can make a selection. Obviously this renders the application useless.

This appears to be a persistent, structural issue that spans different Ubuntu Host OS, different Win Guest OS and h/w architectures.

[federbear]

I have installed the new version (5.1.18) and experienced that I can not select anything in the Virtualbox toolbar when a guest is running in full screen mode. Rolling back to 5.1.10. There is no problem with the mouse.

Host: OpenSuse Leap 42.2
Guest: Windows 7 Ultimate.
The latest guest addition is installed.