There's a few people having issues with keyboards. Unfortunately it's out of my power and is because of Unity's crappy input manager, I'll have to implement my own input manager later down the line. Does your keyboard have anti-ghosting by any chance? I've found that this could be the culprit of keyboard input issues.
Will add it in, won't take much effort
I've finished the update for Physics Test 4, see the post here if you want to see it.