Dear Maintainer,


Create a xmodmap file "~/.xmodmap" and run "Xmodmap ~/.xmodmap". The file
contains some modification to key mappings. The one I used to reproduce this
issue is:
--------------BEGIN XMODMAP------------------
remove mod1 = Alt_L
remove mod1 = Alt_R
remove Control = Control_L
remove Control = Control_R
keycode 37 = Alt_L
keycode 105 = Alt_R
keycode 64 = Control_L
keycode 204 = Control_L
keycode 108 = Control_R
add Control = Control_L
add Control = Control_R
add mod1 = Alt_L
add mod1 = Alt_R
--------------END XMODMAP------------------

After Re-plugging in the keyboard, everything in the xmodmap file was lost.

Also, a similar bug is reported to Ubuntu:
https://bugs.launchpad.net/ubuntu/+source/xorg-server/+bug/287215