A 41-year-old female presents 11 months after laparoscopic Roux-en-Y gastric bypass with 3 months of epigastric pain, hematemesis, and iron-deficiency anaemia. She continues smoking and occasionally takes NSAIDs despite counselling. Upper GI endoscopy reveals a 12 mm ulcer on the jejunal side of the gastrojejunal anastomosis with a white fibrinous base, punched-out margins, and an adherent clot. The structure marked **A** in the diagram is identified. Which of the following is the MOST IMPORTANT modifiable risk factor contributing to the development of this lesion in this patient?