There are limits on the size of attachments that you can send via email. Each mail service can have different limits and they are usually not that big. This means that large set lists and large files cannot be sent via email. In addition, the iPad doesn’t have a lot of working memory so it may run out of memory when creating the zip files necessary. If you need to share large set lists, it’s best to use Airdrop to send to other users. You can also airdrop to a Macintosh and then share using various methods.
If you have a problem with a file and it is repeatable. You can email the file and all of it’s associated files by choosing Settings->File->Email a ZIP of this file.