Work Out Why This Error Keeps Happening

The same error keeps resurfacing no matter how many times you patch around it, because the patch was never the fix. This ranks the likely root causes, explains why this specific trigger produces this specific error, and suggests a test to confirm the cause before you commit to fixing it properly.

<context>
You keep hitting the same error and previous fixes have only masked it temporarily. The error message is: {ERROR_MESSAGE}. It happens when [describe the trigger, e.g. submitting a form twice quickly].
</context>

<task>
**Diagnose the root cause, not just the symptom:**
1. List the three most likely root causes ranked by probability
2. For the top cause, explain the mechanism in plain terms: why does this specific trigger produce this specific error
3. Suggest a fix for the root cause, distinct from any workaround already tried
4. Suggest one test that would confirm or rule out the top cause before you commit to the fix
</task>
<output_format>
Ranked list of causes, then a Diagnosis section, then a Fix section, then a one-line Test to Confirm.
</output_format>