How can I identify the specific node causing the JSON parameter error in my n8n Docker container?

Based on the error stack trace, the issue is happening during execution of an HTTP Request node. In particular, the stack trace shows the error originates from the HttpRequestV3 node (at the file path …/n8n-nodes-base/dist/nodes/HttpRequest/V3/HttpRequestV3.node.js) and then propagates up to the workflow execution. This indicates that one of your HTTP Request nodes is configured with a JSON parameter that isn’t valid JSON.

Here are some steps to help pinpoint and resolve the problem:

1. Identify Affected Node:
   • Since the error message is triggered when executing an HTTP Request node, review workflows that use the HTTP Request node.
   • Look for nodes where the body is specified in JSON; check for common mistakes such as extra commas, missing quotation marks, or incorrect placement of curly braces.

2. Validate the JSON Parameter:
   • Copy the JSON snippet you are passing to the node and run it through a JSON validator or linter.
   • Remember, if you’re using an expression to generate the JSON (wrapped in double curly braces), ensure that the ultimate result resolves to a proper JSON structure.

3. Check Node Configuration in the Editor:
   • Open the workflow in the n8n Editor.
   • Locate the HTTP Request nodes, and review the “JSON” or “Body” parameter configuration.
   • If you recently made changes, ensure these changes haven’t introduced an invalid format.

4. Improve Error Visibility:
   • If you haven’t already, consider enabling the error output on the node (using the “continueErrorOutput” setting) so that you can capture additional context during test runs.
   • This can help you to see the exact data being passed and where it might be failing.

5. Double-Check Container Persisted Files (if applicable):
   • While the error itself is about JSON validity, if you are seeing repeated errors after container restarts, make sure your Docker container’s volumes (like the persisted ~/.n8n directory) are set properly so your workflow files and node configurations aren’t lost or corrupted.

This error doesn’t come from a background process or a system-level issue; it’s specifically coming from the HTTP Request node while it’s attempting to process the JSON parameter. Focusing on that node’s configuration should help resolve the issue.

If after validation the JSON looks correct but the error persists, consider testing the node in isolation (possibly by creating a simplified workflow) so that you can rule out interference from other parts of the workflow.

Let me know if you need further details on any of these steps!