I have recently noticed that for some reason when pressing CTRL in a VM in VirtualBox it doesn't get through… So I can't easily copy and paste etc, it just doesn't get through, the VM doesn't think that I've pressed anything when I press CTRL or at least it doesn't do anything, why is this? It doesn't seem to matter what I run as guest, and it didn't happen before with these same VMs so it's not that they all just don't like it, the problem probably is with VirtualBox. I have tried running Ubuntu GNOME 15.10, Ubuntu 16.04, and Ubuntu GNOME 16.04.
Information Update:
Neither the left, nor the right CTRL keys actually do anything, they don't even seem to interact with Virtual Box because pressing the right one should change something in it.
I have tried installing the Guest Additions CD in my VMs, but it makes no difference to my problem.
OS Information:
No LSB modules are available.
Distributor ID: Ubuntu
Description: Ubuntu 15.10
Release: 15.10
Codename: wily
Flavour: GNOME
GNOME Version: 3.18
Package Information:
Version: 5.0.14 r105127
Best Answer
I have figured out the problem!
The problem was that for some reason when one has the
Show location of pointeroption enabled in thegnome-tweak-tool, as this is assigned to CTRL, for some reason this prevents programs from capturing this key. So disabling that option in thegnome-tweak-toolfixes the issue.