I have problems changing the grid size: sometimes I can change only the width, sometimes it doesn't work at all.
Not sure this is what you mean, but changing these have as far as I know always been a bit weird as these boxes doesn't react to you pressing enter. So try this instead, after you have change one of the values just select the other textbox and it should work, sometimes you have to do it a few times just clicking between the two boxes after you have change the values and it sticks (works). Whether its a bug or simply just weird I don't know, but they surely work in mysteries ways