A 28-year-old female from Delhi sustained a simple fracture of the radius and ulna 3 weeks ago. She was treated with open reduction and internal fixation (ORIF) using plates. At the 3-week follow-up, X-rays show minimal callus formation around the fracture site, and the fracture line remains clearly visible. Clinically, there is still moderate pain and swelling, and the arm cannot bear weight. Which of the following best explains the radiological findings at this stage?