Comment 11 for bug 281669

I believe this is a BIOS issue.

I have fixed it by entering the BIOS (pressing the blue ThinkVantage button during boot) and editing the following configuration:

Hit F1 to enter the BIOS Setup Utility
Enter: 'Config' menu ->
Enter: 'Keyboard/Mouse' menu ->
Edit: 'ThinkPad NumLock' [from Independent to Synchronized]

Reboot the computer and run:
  sudo input-events -t30 3" and press "Fn+NmLk

You should receive outputs for each press:

/dev/input/event3
   bustype : BUS_I8042
   vendor : 0x1
   product : 0x1
   version : 43860
   name : "AT Translated Set 2 keyboard"
   phys : "isa0060/serio0/input0"
   bits ev : EV_SYN EV_KEY EV_MSC EV_LED EV_REP

waiting for events
11:58:52.899591: EV_SYN code=0 value=0
11:58:56.004989: EV_MSC code=4 value=69
11:58:56.005006: EV_KEY KEY_NUMLOCK (0x45) pressed
11:58:56.005012: EV_SYN code=0 value=0
11:58:56.005439: EV_LED code=0 value=1
11:58:56.060590: EV_MSC code=4 value=69
11:58:56.060604: EV_KEY KEY_NUMLOCK (0x45) released
11:58:56.060609: EV_SYN code=0 value=0
11:58:57.262065: EV_MSC code=4 value=69
11:58:57.262080: EV_KEY KEY_NUMLOCK (0x45) pressed