There are a few reasons why this can happen (we're working on more specific error messages), so here are a few things to try when troubleshooting:
- Try disabling auto-save (tap the title header > tap Disable Auto-Save.
- Try changing the name of the file slightly (e.g. add a number to the end).
- Try emailing one of these as an annotate file, then saving that copy.
- Try saving the file to another storage location.