Lexmark CX725
Remove the front cover. See Front cover removal.
Remove duplex inner guide. See Duplex inner guide removal.
Remove the pivot shaft. See Pivot shaft removal.
Remove the tray indicator (A).
Remove the 12 screws (B), and then remove the duplex outer guide.
Print Quality Diagnosis ‑ Sample defects with print quality test pages
Lexmark CX/CS8xx_72x and XC/Cxxxx: Faded Print in Duplex Scenarios