Cleaning a CSV before JSON conversion

Confirm the delimiter, header row, and quoting rules before changing data. A comma inside a quoted value is not a new column, and an embedded newline may be valid if properly quoted.

Use a small copy with a normal and a troublesome row. Check duplicate or empty headers, blank fields, and consistent date formats. Convert the sample, then compare output rows and value types with the source before processing the full file.

What is the first row that converts incorrectly?