Repeat keys doesn't work after upgrade from 17.04 to 17.10

Question

I use a laptop with Xubuntu. I upgraded from 17.04 to 17.10 recently. Since the upgrade, the repeat keys functionality doesn't work.

By repeated keys I mean: when pressing one key and holding it down, I expect that the letter associated with the key will appear again and again on screen until I stop pressing the key.

However, the witnessed behaviour is the following: when pressing one key and holding it down, the letter is printed between 1 and 4 times and then it stops.

Things I have done without any positive result:

• Searched here and in other websites for other instances of this same problem.
• Ensured that the Repeat keys checkbox is enabled in Settings > Keyboard > Behaviour.
• Disabled and enabled again the Repeat keys checkbox.
• Experimented with different values of Repeat delay and Repeat speed on the same configuration screen.
• Tried another keyboard connected by USB.
• Used xkbset repeatkeys to disable and enable the repeat keys.
• Used evtest to see the events of the keyboard and saw nothing unusual.

Any ideas on what could be the problem, and hopefully how to fix it?

EDIT 1:

I have edited the original text to clarify that the letter is repeated between 1 and 4 times and then it stops.

As requested in the comments, output of a couple of commands:

$ gsettings get org.gnome.desktop.peripherals.keyboard repeat
true
$
$
$ xset q r
Keyboard Control:
  auto repeat:  on    key click percent:  0    LED mask:  00000002
  XKB indicators:
    00: Caps Lock:   off    01: Num Lock:    on     02: Scroll Lock: off
    03: Compose:     off    04: Kana:        off    05: Sleep:      off
    06: Suspend:     off    07: Mute:        off    08: Misc:       off
    09: Mail:        off    10: Charging:    off    11: Shift Lock: off
    12: Group 2:     off    13: Mouse Keys:  off
  auto repeat delay:  467    repeat rate:  29
  auto repeating keys:  00ffffffdffffbbf
                        fadfffefffedffff
                        9fffffffffffffff
                        fff7ffffffffffff
  bell percent:  50    bell pitch:  400    bell duration:  100
Pointer Control:
  acceleration:  2/1    threshold:  4
Screen Saver:
  prefer blanking:  yes    allow exposures:  yes
  timeout:  900    cycle:  0
Colors:
  default colormap:  0x40    BlackPixel:  0x0    WhitePixel:  0xffffff
Font Path:
  /usr/share/fonts/X11/misc,/usr/share/fonts/X11/Type1,built-ins
DPMS (Energy Star):
  Standby: 600    Suspend: 600    Off: 600
  DPMS is Disabled

And another weird thing that I have found since writing this, which may or may not be related to the above problem:

When pressing an accent key just once, if I don't press any other key immediately a weird letter appears by itself. For example, if I press the key ´ (0xB4) once and don't press anything else immediately the character ΰ (0x3B0) appears by itself. It happens also with other accents like ` and ^.

EDIT 2:

The issue happens with any keyboard: either the builtin keyboard of the laptop, or a USB keyboard. In the case of the USB keyboard, I tried different ports and cables and the result is the same.

EDIT 3:

Two more tests:

• Changed to another tty (e.g. Ctrl+Alt+F5) and there I could see that ^@ was constantly being printed without pressing any key. This is one of the representations of the NULL character.
• Booted from old live USBs containing Xubuntu 17.04 and 16.04 (latest LTS) and the problem did not manifest there: repeat keys worked perfectly

EDIT 4:

Final test:

• Booted from live USB containing Xubuntu 17.10 and the problem shows up again.

Answer 1

You said: ^@ was constantly being printed withou pressing any key, this suggests driver problem.

lsmod | grep wmi

If peaq_wmi is present do with sudo:

modprobe -rv peaq_wmi

If it works properly become permanent by adding to blacklist:

nano /etc/modprobe.d/blacklist.conf

blacklist peaq_wmi