Contradiction of stronger transmitters: a report differs from a better-preserved version, requiring comparative criticism.
Weak retention: a narrator demonstrates a meaningful pattern of mistakes or inadequate precision.
Ikhtilāṭ: a serious later deterioration after a period of reliable transmission, requiring chronological separation of auditions.
These factors may co-occur: a late report from a confused narrator can conflict with the version of a highly precise transmitter. But their possible overlap does not make their definitions identical. Sound grading identifies precisely what evidence establishes the defect.