I looked carefully at page 32 of the manual for the 2400RDS. It is indeed different from the instructions for the 2400U, the US model.

Have you tried following directions but NOT pushing the up and down buttons? The directions tell you to push the left and right buttons, but they do not tell you to push the up and down buttons.

You say that when you "press the arrow keys up/down left right" that you have a problem. Try following the instructions EXACTLY and just pressing the left and right buttons, that is, - and + , not up or down. Perhaps there is a problem with freezing up if you hit those buttons, but the Yamaha crew did not happen to hit those buttons in their tests so they did not find that problem.

Yamaha have made this more confusing by telling you to push buttons with symbols of a left-facing and a right-facing triangle, although the buttons are actually labeled - and + . Whenever I see a totally dumb oversight like that, I find it hard to believe that the same crew got everything else right.