By default, because VorpX uses head-tracking to control where you’re looking by generating virtual mouse movements, it also has to emulate the controller – I think Fallout 4, like many games, doesn’t allow simultaneous mouse and conroller input.
However, there is an experimental feature in VorpX for Fallout 4 only which gets round this. Call up the Vorpx in-game menu (default key is ‘Delete’), use the left/right arrow keys to get to the head-tracking menu, then down arrow to ‘Start direct tracking scan’ and enter. After a pause and a hitch in your view it’ll suddenly rotate your character. Ten you’ll probably find head-tracking is more accurate, and also that the controller works as intended.