How are you opening/transferring it? Does your notes field have rich-text formatting enabled? If so, you might try disabling it or wrapping everything in quotes.
Invaluable tool for checking (and repairing) CSV files. https://csveasy.com/
You can try running REGEX_REPLACE({field},"\n"," ") or if its stubborn like in my case REGEX_REPLACE(REGEX_REPLACE(REGEX_REPLACE(REGEX_REPLACE(REGEX_REPLACE(REGEX_REPLACE(REGEX_REPLACE({Field},"\r"," "),"\n"," "),"\r\n"," "),"u2028"," "),"u2029"," "),"u0085"," "),"u00B6"," ")
This took care of most of the line breaks but there are still 2 stubborn line breaks I cannot beat HELP!
You can basically use the app "Excel-Exporter" to avoid troubles and to save time. They have a freemium version and a premium version with a 7 days free trial.
Just in case: https://excel-exporter.com/dashboard/app
csvgetter.com is a tool specifically designed for airtable export and automation. Its very easy to use, powerful and secure - and there are loads of help + advice docs. Let me know what you think