(If I move the guest VM to a windows 7 host this doesn't happen, so for now I'm presuming it to be host issue rather than a guest issue)
Host OS is Oracle Linux 7.4. Guest OSs are Windows 7 64-bit, Windows 10 LTSB, Server 2008 and Server 2012.
If I 'minimize' a full-screen guest, when I open it back to full-screen the video is now 'offset' by about 1/2" downwards (on a 22" screen). That is to say, the full-screen video now has a gap of about 1/2" at the top and if I want to click on an object on the guest screen with the mouse I have to aim the mouse pointer about 1/2" above where it should be. To get the full-screen back to normal I have to use Ctrl-F to toggle to "windowed" then Ctrl-F again back to Full Screen.
This 'offset' only happens when toggling between full screen and minimized, not when toggling between windowed and full-screen.
I can replicate this on two different sets of hardware for the host, a Lenovo ThinkCenter M93 workstation and a Panasonic Toughbook CF-C1 laptop. Both have Intel integrated video - Intel Q95 Haswell chipset on the Lenovo and Intel QM67 on the Panasonic.