When you practice are you using the same posture that you use when you are in rehearsals or concerts? Is your head in the same position? How about the angle of the oboe and reed? I’ve noticed that so many of my students have their heads down further than they should be during the start of their lessons, when they are doing long tones and scales. They are looking down much of the time. When I ask if that’s how they sit and hold their heads when they are in rehearsals and concerts they say no. Reeds react differently if we have a different angle. Try to practice with a consistent angle, and use the one you use when at orchestra or band rehearsal.
Oh, and “I always do that!” is not permission to “always do that.” As I tell my students, a conductor would not respond well to me if I made a mistake and said, “I always do that!” as if that somehow makes it acceptable or at least expected. Don’t give yourselves permission to “always do that.” Fix it!