What is the main issue when a debt in sound coins is paid using debased coins?

Performance and Substitution: Complete and Deficient Adāʾ and Qaḍāʾ

• Treating the debased payment as return of a specific usurped item
• Treating coin count alone as replacing all required qualities
• Deficiency in the required quality
• Assuming the debt is automatically extinguished by substandard coins