Not working input button spacebar, if press and hold buttons arrow!

Not working press spacebar, if press and hold buttons arrow!

1. Press and hold the button right arrow + up arrow, and press the spacebar. Console to write a "Space"
2. Press and hold the button left arrow + up arrow, and press the spacebar. Console NOT write a "Space"
3. Press and hold the button left arrow + bottom arrow, and press the spacebar. Console NOT write a "Space"
3. Press and hold the button right arrow + bottom arrow, and press the spacebar. Console NOT write a "Space"

Unity 5.5.0p4

script c#
...
void Update () {

if (Input.GetKeyDown(KeyCode.Space))
{
print("Space");
}
}

 

Something tells me this is a key matrix problem

 

Other keys work! On the other keyboard the same problem!

 

The problem is not in Unity! https://www.microsoft.com/appliedsciences/KeyboardGhostingDemo.mspx
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