We are sorry for the trouble. Would you mind sharing the workflow/steps you are doing to export the PDF to Excel?
Do you have Adobe Export PDF plan and unsing Adobe Acrobat Reader to use the export function? If yes what is the version of the Adobe Acrobat Reader DC? To check the version go to Help > About Adobe Acrobat Reader DC
And make sure you have the latest version 20.009.20067 installed. Go to Help > Check for Updates
Also, is this a behavior with a particular PDF file or with all the PDFs? Please try with a different file and check