These started appearing in the logs as of 19:07 on 20th June 2018
First apparent occourance: https://logstash.wikimedia.org/app/kibana#/doc/logstash-*/logstash-2018.06.20/mediawiki/?id=AWQemKHcoOODFPKv_v5c
It looks like it is happening at a pretty regular interval https://logstash.wikimedia.org/goto/87b5d23390f454cbeed31066d6b4ce1e
```
Exception executing job: cirrusSearchLinksUpdate Property:P399 addedLinks=[] cluster=codfw removedLinks=[] requestId=9d506fbd1f4ec71ac82ddd99 : Wikibase\DataModel\Services\Lookup\PropertyDataTypeLookupException: Property data type lookup failed for: P400
&
[9d506fbd1f4ec71ac82ddd99] /rpc/RunSingleJob.php Wikibase\DataModel\Services\Lookup\PropertyDataTypeLookupException from line 50 of /srv/mediawiki/php-1.32.0-wmf.999/vendor/wikibase/data-model-services/src/Lookup/EntityRetrievingDataTypeLookup.php: Property data type lookup failed for: P400
```
Stacktrace:
```
#0 /srv/mediawiki/php-1.32.0-wmf.999/vendor/wikibase/data-model-services/src/Lookup/EntityRetrievingDataTypeLookup.php(37): Wikibase\DataModel\Services\Lookup\EntityRetrievingDataTypeLookup->getProperty(Wikibase\DataModel\Entity\PropertyId)
#1 /srv/mediawiki/php-1.32.0-wmf.999/extensions/Wikibase/lib/includes/PropertyInfoDataTypeLookup.php(53): Wikibase\DataModel\Services\Lookup\EntityRetrievingDataTypeLookup->getDataTypeIdForProperty(Wikibase\DataModel\Entity\PropertyId)
#2 /srv/mediawiki/php-1.32.0-wmf.999/vendor/wikibase/data-model-services/src/Lookup/InProcessCachingDataTypeLookup.php(38): Wikibase\Lib\PropertyInfoDataTypeLookup->getDataTypeIdForProperty(Wikibase\DataModel\Entity\PropertyId)
#3 /srv/mediawiki/php-1.32.0-wmf.999/extensions/Wikibase/repo/includes/Search/Elastic/Fields/StatementsField.php(130): Wikibase\DataModel\Services\Lookup\InProcessCachingDataTypeLookup->getDataTypeIdForProperty(Wikibase\DataModel\Entity\PropertyId)
#4 /srv/mediawiki/php-1.32.0-wmf.999/extensions/Wikibase/repo/includes/Content/EntityHandler.php(763): Wikibase\Repo\Search\Elastic\Fields\StatementsField->getFieldData(Wikibase\DataModel\Entity\Property)
#5 /srv/mediawiki/php-1.32.0-wmf.999/extensions/CirrusSearch/includes/Updater.php(343): Wikibase\Repo\Content\EntityHandler->getDataForSearchIndex(WikiPage, ParserOutput, CirrusSearch)
#6 /srv/mediawiki/php-1.32.0-wmf.999/extensions/CirrusSearch/includes/Updater.php(396): CirrusSearch\Updater::buildDocument(CirrusSearch, WikiPage, CirrusSearch\Connection, integer, integer, integer)
#7 /srv/mediawiki/php-1.32.0-wmf.999/extensions/CirrusSearch/includes/Updater.php(204): CirrusSearch\Updater->buildDocumentsForPages(array, integer)
#8 /srv/mediawiki/php-1.32.0-wmf.999/extensions/CirrusSearch/includes/Updater.php(83): CirrusSearch\Updater->updatePages(array, integer)
#9 /srv/mediawiki/php-1.32.0-wmf.999/extensions/CirrusSearch/includes/Job/LinksUpdate.php(52): CirrusSearch\Updater->updateFromTitle(Title)
#10 /srv/mediawiki/php-1.32.0-wmf.999/extensions/CirrusSearch/includes/Job/Job.php(98): CirrusSearch\Job\LinksUpdate->doJob()
#11 /srv/mediawiki/php-1.32.0-wmf.999/extensions/EventBus/includes/JobExecutor.php(67): CirrusSearch\Job\Job->run()
#12 /srv/mediawiki/rpc/RunSingleJob.php(80): JobExecutor->execute(array)
#13 {main}
```