Find out why an integration drops, duplicates or rejects events before commissioning a wider repair. Starting estimate: US$200 for one agreed issue in one API or webhook flow. We confirm the scope, acceptance criteria and funded milestone before work begins. You receive: • An investigation of the relevant code, API documentation and redacted logs in an isolated or staging environment. • A reproducible failure case when the supplied evidence permits it, with a concise explanation of the findings. • A proposed repair and focused regression tests when the failure can be reproduced. Implementation beyond the diagnostic scope is quoted separately. • A handover covering what was verified, remaining uncertainties and the next action. If the issue cannot be reproduced, the report documents the attempted checks and the additional evidence needed. Good starting cases include signature mismatches, duplicate processing, failed callbacks and unsafe retries. Please send the affected flow, expected versus actual behavior, relevant documentation and redacted errors. Do not send passwords or payment credentials in the initial message. Delivery is normally three business days after complete inputs, agreed scope and funding. One clarification round is included. Production changes, live financial transactions and continuing support require a separate agreement. The linked demonstration includes public source, nine passing tests and verification notes covering signed-event validation, duplicate events, SQLite persistence and uncertain provider outcomes. It uses synthetic orders and a simulated provider. Its README explains the tested scenarios and the additional checks needed for a real integration. Each delivery identifies the checks performed, findings and remaining limitations.