This question already has an answer here:
Just moved from Unity to GNOME and faced such problem:
I change keyboard layouts by Ctrl+Shift. Often use console and when I press Ctrl+Shift+C/V (or any other combinations, where there are Ctrl and Shift), GNOME also changes keyboard layout language.
In Unity, and in Windows, the computer normally waits whether I add to the combination any additional keys or release at least one of the keys (Ctrl/Shift) in order to change the language. GNOME, in my case, changes the language immediately once Ctrl+Shift are pressed.
I have Ubuntu GNOME 16.04, x64 (Fresh installation, downloaded from https://ubuntugnome.org)
Can anyone suggest how to fix this?