Here are a list of things to check that may solve this issue. Please note that you can always easily save all your files to a Mac or PC, here’s how: How to export all Locker files to Mac or PC
Things to check:
- Go to Settings app > Storage and make sure your storage is not too full
- If your collection includes some large files like long videos, export them individually and then delete them, then try exporting the rest.
- If Export All Files is giving an error, you can still save your files to a Mac or PC by viewing the link above.
You can also export files individually by holding down on them and choosing "Send / Share".