If a wrong delimiter is guessed by the importer and the file contains quotes like this .txt file with commas as delimiter:
Row1,
Row2,"|""|"
Row3,"|""|"
...

The “new” importer will create a single row for Row2 and Row3 including extra columns.
This means the entire file will be displayed in the sample:
image1056×314 13.2 KB
For a large enough file this results in the importer loading forever (the loading time grows exponentially with the file size).

Originally reported on https://forums.ankiweb.net/t/bug-with-importer-for-files-containing-quotes/51732/2