URLs like https://www.wikidata.org/wiki/Special:EntityData/Q4115189.ttl?flavor=dump are cached by Varnish but when action=purge is issued, they are not purged since EntityDataUriManager::getCacheableUrls does not account for query parameters. Thus, if the content of Q4115189 is modified, even after purge action it may remain cached and contain stale data.
We need to either fix purge operation to account for flavors (preferably) or disable caching of flavor URLs.