Multiple upload field bug (Wordpress 4.0)

I'm trying to add multiple upload field to my custom post type. But when post is published/updated instead of one upload field I get two one of them contains atachment id an the other file path as a value.

Start by reproducing the multiple upload field behavior in a custom post type on WordPress 4.0, using the screenshot and issue description as the expected scenario. Trace the field's publish or update handling; done means the custom post type retains one upload field rather than creating separate attachment-ID and file-path values.

Written by the indexing model from the issue text.