Example from logs:
2013-07-15 17:39:02 mw1198 wikidatawiki: [5d761328] /w/api.php?action=wbeditentity&format=xml Exception from line 1699 of /usr/local/apache/common-local/php-1.22wmf9/includes/GlobalFunctions.php: Internal error in ApiFormatXml::recXmlPrint: (de, ...) has integer keys without _element value. Use ApiResult::setIndexedTagName().
Possibly related to change Ib954536e5:
https://gerrit.wikimedia.org/r/#/c/73322/1/repo/includes/api/EditEntity.php
Version: unspecified
Severity: major