All the buttons in the "Activity" page are only Alias'es
pointing to the button with actual code stored in it....
sometimes the software points to a blank button or no
button at all.... doesnt happen very much but there is
a fast and easy fix.... go to the "tune Up" menu then
go to the "Copy a command from a device and paste ity
into another Device or Activitey"... then select the Device
with the button you wish to copy... highlight it then
press the "copy" button... next use the drop down menu
again to select the activity with the button in question....
highlight it and press paste... there you go.. you should
now have a correct Alias for that button.... this is all
assuming that the button in the actual device works..
but as you said it does.... this should fix your problem