VNC: pressing Shift + Tab = Tab only

I'm using VNC to access an Ubuntu 16.04 laptop (running Desktop Sharing) from a Windows 10 desktop (running Ultra VNC Viewer). My problem: some keyboard combos don't travel well; for example, pressing Shift+Ctrl+Tab is processed on the server as Ctrl+Tab.

The problem persists when using a different VNC client, for example MobaXTerm, so the issue seems to be on the Ubuntu side. How can I solve this? Thanks.

Solution 1:

Instruction from this (2009) thread solved the issue for me: https://bugzilla.gnome.org/show_bug.cgi?id=353304#c21

Solution: Run in Ubuntu terminal: xmodmap -e 'keycode 23 = Tab'

EDIT: to make the fix permanent (for 18.04) run sudo vim /usr/share/X11/xkb/symbols/pc and change the line

key <TAB> { [ Tab, ISO_Left_Tab ] };

to

key <TAB> { [ Tab ] };

After that reboot.