How quotes break CSV
A quoted field may contain commas and line breaks. The field ends at the next quote that is not doubled. If that quote is missing, every later row is swallowed. If a quote appears in the middle of an unquoted city name, some parsers abort.
How this fixer works
It parses leniently, records unclosed and bare quotes, then writes a strict CSV: fields that need quoting are wrapped, and interior quotes become two quotes. Multiline comments remain multiline, still quoted.
Example
Malformed input:
id,name 1,"Anne
Repaired:
id,name 1,"Anne"
Limitations
Recovery cannot know where a missing quote should have been if the author intended to close it mid-row. Inspect the preview when the unclosed-quote error points at row 1 and the file has hundreds of lines.