...
The error is caused by non-standard handling of UTF-8 characters. It is commonly associated with Microsoft Excel.
To resolve, upload your file to Google Drive, converting to a Google Spreadsheet doc, then download as CSV:
...
Upload your file to Google Drive with settings to convert uploads checked.
...
Download the new Google Spreadsheet as CSV.
...
Create a new ingestion using the CSV file downloaded from Google Drive.
...
we recommend using Google Docs to create the CSV file.