This is a weird one and only appears to affect Scaffold, not (at least in my testing) the same translator running in the browser.

The DOI translator is completely broken when run inside Scaffold in Zotero 7: It detects the DOIs, but it then almost seems like the functions aren't firing in the correct order -- in any case, the select item dialog is never displayed and the translator just ends with Translation successful and no imports.
E.g. on http://blog.apastyle.org/apastyle/digital-object-identifier-doi/ but appears to happen everywhere.