ghosting

The practice of hiding prisoners from inspection from (possibly hostile) outside inspectors.

The blurry appearance of a television picture resulting from interference caused by multipath reception.

Ghost imaging.

A form of identity theft in which someone steals the identity, and sometimes even the role within society, of a specific dead person (the "ghost") who is not widely known to be deceased.

A problem with a keyboard where certain simultaneous keypresses trigger the action of a further key that was not in fact pressed.

Examine your matrix map, and make sure that no three keystrokes form a rectangle with a fourth keystroke that will cause you problems. This prevents both ghosting and blocking.