I'm assuming what's happening is when he's rotating it and changing pivot points that it's changing the X,Y,Z, so one time pressing an arrow key rotates the block in one direction but then pressing the same arrow key will rotate it in a different direction. There's a few blocks that it can happen with because the shape has similar sides. It's just one of those things that takes a couple of different circumstances happening at the same time to cause it, easily fixed with either backspace and or a double press of enter key.
Could be. As i understood it he meant though that once he is looking from the left side on it and the left arrow key will rotate it to the right. Next time he is lining from the right on it and the left arrow key will rotate it now to the right.
Is a matter of the settings, not a game issue