Why is GA4 counting my conversions twice and how can I fix it?

Topic summary

GA4 (Google Analytics 4) is recording conversions twice on the checkout page in a Payments + Shipping & Fulfilment context (tagged: checkout).

Setup: The merchant has the Google & YouTube app installed with conversion tracking active, and additional tracking code attached to the checkout page.

Problem: Conversions are being counted two times; the user asks how to prevent this double counting.

Artifacts: A code snippet is referenced as central to diagnosis, but its content is not provided.

Outcome/Status: No solution or action items are documented; the discussion remains open with the cause undetermined due to missing implementation details.

Unanswered key questions: Which specific events are fired on the checkout page, how many times are they triggered, and whether both the app and custom code are sending the same conversion event.

Summarized with AI on January 14. AI used: gpt-5.

Google & YouTube app installed and conversion tracking active,
Also, the following codes are attached on the checkout page,

Conversions are counted two times, how can I avoid this?