Gnome Software keyboard weirdness

I also had this problem, did some searching and found this. It fixes the issue for me no longer getting double letters

Install ibus-gtk In the terminal do

sudo apt-get install ibus-gtk ibus-gtk3

Reboot. (Does not work until rebooted)

Should work now!

I had the same problem after upgrading to 16.04.

I had previously disabled IBus when I was running <=15.10 due to an issue with the Jetbrains Pycharm IDE.

Renabling IBus fixed the issue with Gnome Software for me.

Try opening your system Settings ­> Language Support and ensuring the Keyboard input method at the bottom of the page is set to ibus. If it was set to none, reboot after you change the setting.