The https://logstash.wikimedia.org/#/dashboard/elasticsearch/resourceloader dashboard is filled with almost exclusively errors from MultimediaViewer about non-existent message keys being referenced.
MessageBlobStore::fetchMessage failed to find: 'multimediaviewer-option-header-viewer' (pt-br) MessageBlobStore::fetchMessage failed to find: 'multimediaviewer-option-header-filepage' (pt-br) MessageBlobStore::fetchMessage failed to find: 'multimediaviewer-option-desc-viewer' (pt-br) MessageBlobStore::fetchMessage failed to find: 'multimediaviewer-option-desc-filepage' (pt-br) MessageBlobStore::fetchMessage failed to find: 'multimediaviewer-license-cc-by-sa-3.0-migrated' (pt-br) MessageBlobStore::fetchMessage failed to find: 'multimediaviewer-description-page-popup-text-local' (pt-br) MessageBlobStore::fetchMessage failed to find: 'multimediaviewer-option-header-viewer' (zh) MessageBlobStore::fetchMessage failed to find: 'multimediaviewer-option-header-viewer' (ja) MessageBlobStore::fetchMessage failed to find: 'multimediaviewer-option-header-filepage' (zh) MessageBlobStore::fetchMessage failed to find: 'multimediaviewer-option-header-filepage' (ja) MessageBlobStore::fetchMessage failed to find: 'multimediaviewer-option-desc-viewer' (zh) MessageBlobStore::fetchMessage failed to find: 'multimediaviewer-option-desc-viewer' (ja) MessageBlobStore::fetchMessage failed to find: 'multimediaviewer-option-desc-filepage' (zh) MessageBlobStore::fetchMessage failed to find: 'multimediaviewer-option-desc-filepage' (ja) MessageBlobStore::fetchMessage failed to find: 'multimediaviewer-license-cc-by-sa-3.0-migrated' (zh) MessageBlobStore::fetchMessage failed to find: 'multimediaviewer-license-cc-by-sa-3.0-migrated' (ja) MessageBlobStore::fetchMessage failed to find: 'multimediaviewer-description-page-popup-text-local' (zh) MessageBlobStore::fetchMessage failed to find: 'multimediaviewer-description-page-popup-text-local' (ja)
At least multimediaviewer-option-header-viewer doesn't seem to exist at all in i18n/en.json and was probably deleted at some point. I haven't checked the others.