When a narrator is described only as “laysa bi-thabt,” which more serious accusation cannot properly be inferred from that description alone?

Narrator Criticism, Integrity and Precision: Standards of Scholarly Appraisal

• There is a reservation about his firmness of retention and transmission
• The expression raises concern about his precision in hadith
• He knowingly fabricated reports and attributed them to the Prophet
• Assessing the precision of his transmission is necessary before relying on it