If you can’t find anything wrong with the primary file lines with error reports, trace errors with the following procedure:
Error reports can now be eliminated. However, if errors are still reported, the errors are in the previous lines. The errors in the previous lines did not stop the importing, but did cause problems in the next lines.
The error reports can now be eliminated.
Once you identify the problem lines, see how they differ from lines that were successfully imported, or how they differ from the proper migration file format.