I accidentally discovered a fix for this while trying to solve a different problem.


find the line

< property name="&lt;Super&gt;Tab" type="string" value="switch_window_key"/>

and change it to

< property name="&lt;Super&gt;Tab" type="empty"/>

reboot or whatever and then tab will work properly!

I have no idea why but when using vnc this file seems to override tab's normal behaviour and makes it into a switch window key.