When I access the "Tome of power" on my Psyker I am able to utilize the down function (Via D-pad or joystick) on the Biomancy, Divination and Telekinesis trees. This applies to editing my masteries as well, however when I go to the Pyromancy tree I am stuck and unable to utilize the "Down" functionality. This can be remedied by cycling fairly quick through the other trees back to Pyromancy but it does not always work. The issue carries over into trying to edit the masteries on any pyromancy skill as well. As you can imagine this makes selecting new skills and masteries very difficult.
If any more information is needed or you are experiencing this issue on Xbox one as well please let them know here.