Comment 3 for bug 362455

An improvement to the duplicate key presses appears to be the following:

# force a different rate using an xserver command, setting the rate to 25 characters per time unit, starting to repeat after 300 milliseconds
sudo kbdrate -r 25 -d 300

This will only work for your current login. Also it appeared to either take some internal defaults ignoring the settings you provide, or it only changes the settings once - every additional change has no effect, although it claims to have changed the values accordingly.

If the xfce ( I am using this window manager ) repeat speed settings are adjusted once more, the configuration changees back to a small repeat delay. If thhe aforementioned command is runn again, it has no efffect.

I was using a relatted bug description to try to figure out a workaround:
https://bugs.launchpad.net/ubuntu/+source/xserver-xorg-input-evdev/+bug/264196