When a teacher's name appears both with early students and with someone of a much later generation, the later chain should not immediately be declared impossible. The categories of sābiq–lāḥiq and unusually long lifetimes may be relevant.
An investigator should ask:
1. Is the supposed common teacher actually the same person?
2. Do the late pupil's birth date and the teacher's death date allow an encounter?
3. Is there evidence that both pupils heard from him?
4. Could the apparent teacher be another person with the same name?
These inquiries connect transmitter biography, chronological reasoning, and isnād criticism.