We ran into an issue with a Excel spreadsheet where pasting text into a field was causing it make the text a formula.

The answer is not use the “@” symbol in the beginning of the text. Some people recommend using an apostrophe or something before the text.  The following link helped us solve this.

https://www.pcreview.co.uk/threads/function-not-valid-getting-rid-of-the-symbol.1763379/

Let us know if this helped you…