Trace this reproducible failure from the user's action through the relevant user interface, route, request, middleware, authentication and authorization checks, service logic, database or file access, and response handling.

Use source code, tests, browser evidence, server logs, and request identifiers to identify where expected and actual behavior first diverge. Build a short sequence diagram in plain language. Rank no more than three hypotheses and cite the evidence supporting and contradicting each one.

Run read-only or non-mutating diagnostic checks first. If a temporary probe or additional logging is needed, describe its exact scope, sensitive-data treatment, performance impact, and removal plan. Wait for approval before modifying code or configuration.