When credible corroboration accompanies a report by someone termed “fīhi ḍaʿf,” what is the first step?

Narrator Generations, Historical Verification, Places of Origin, and Critical Ratings

• Call it ṣaḥīḥ li-dhātihi without inquiry
• Examine the weakness and independence of the routes
• Discard all routes
• Immediately brand the narrator a liar