Pulling to one side when letting go of the hb's may not be alignment at all. I once had this problem, it was the headset. Was too tight. A mechanic adjusted it for me and no mo prollem!

My tandem seemed to pull to the side at one time, even with my hands on the hb's. Turned out the headset had race and bearing problems. Replaced it with a new headset, No mo prollem!

Lift the front end off the ground. Slowly turn the hb's side to side. Is it rough or do you feel a sticky point? If so, could be the headset, maybe adjustment, maybe a scuky headset. Might be something the shop dudes overtightened!