In your second trial, Discourse is skipping the uploads because they already exist in the uploads table. Discourse avoids overwriting existing uploads unless explicitly instructed.
You can try adding the below code snippet in attachment_importer.rb (discourse/script/import_scripts/phpbb3/importers/attachment_importer.rb at main · discourse/discourse · GitHub) before calling @uploader.create_upload will ensure that any existing upload with the same filename is deleted first , forcing Discourse to re-upload it.
existing_upload = Upload.find_by(original_filename: filename)
if existing_upload
existing_upload.destroy
puts "Deleted existing upload: #{filename}"
end
upload = @uploader.create_upload(user_id, path, filename)