Problem with "gnome-terminal" on Gnome 3.12.2

You have to add LANG=en_US.UTF-8 to /etc/default/locale and reboot your system. (Solution from this Arch Linux forum post.)

Here is the list of commands which helps me:

sudo apt install dconf-cli
dconf reset -f /org/gnome/terminal
sudo apt-get remove gnome-terminal
sudo apt-get install gnome-terminal
sudo locale-gen --purge
sudo dpkg-reconfigure locales
reboot

As you can see I just reinstall gnome-terminal

You probably messed around with your locales. Either add LANG=en_US.UTF-8 to /etc/locale.conf and reboot or delete that file altogether (sudo rm /etc/locale.conf && sudo locale-gen en_US.UTF-8 && sudo dpkg-reconfigure locales) and reboot.