When browsing by music folder the alphanumeric keys should (as I understand it) jump to the first folder with the appropriate letter for that button with multiple presses giving access to the other letters on the same button. For me this works fine until I get to the last row of buttons (PQRS TUV WXYZ). Pressing one of these buttons seems to cause it to enter a mode where none of the buttons have the correct behaviour. I'm not sure what exactly is happening but possibly it is using something like 5 -> 50% of the way through the list.