API error responses generated by AbuseFilter and SpamBlacklist have changed, as announced here: https://lists.wikimedia.org/pipermail/mediawiki-api-announce/2019-September/000148.html (relevant task: T229539).
It appears you have special handling for the old responses. It should be updated, otherwise they will probably show a generic error message instead of a more specific one.
extensions/Translate/resources/js/ext.translate.editor.js: 248: } else if ( editResp.spamblacklist ) {