I have noticed the same thing. It looks to me like the reason it learns some buttons and not others is how long the code is broadcasted. One of my other remotes shows how long it is actually sending the signal and there are some signals that continue to send as long as I hold the button and some signals that send for just a second no matter how long I hold the button. The signals that last just a second I can't get the remote to learn. The other signals I don't have a problem with.

I called marantz and they said there was no way to get the signals until the editing software comes out at the end of this month.

I will probably wait it out.