I think that the client may need to save all changes to the the file first before committing to the email action. Otherwise all the values entered in that form just remain in temporary memory and not saved to disk.
I have the same issue where in I receive an older version when a supplier sends me an updated version (via mail) where they have adjusted. However if I open it in windows viewer it shows the updated file. If I open in Adobe Acrobat Standard DC it does not have the updated file rather the previous file.