Create an artifact.
Add an attachment, submit.
Delete an attachment, submit.
Add another attachment, submit.
Export the tracker:
src/utils/php-launcher.sh src/utils/export_project_xml.php \
-p <project-id> \
-u admin \
-t <tracker-id> \
-o /path/to/archive.zip
=> you should not get an error
Import the archive in another project
src/utils/php-launcher.sh src/utils/import_project_xml.php \
-p <another-project-id> \
-u admin \
-i /path/to/archive.zip \
--automap no-email,create:A
=> the artifact is imported. only non-deleted attachments are imported.