You need to use Stale.FALSE to make sure all new documents are included in any view result.
A brief descrition of the Stale options:
TRUE - allow stale results, eg return what is available now
UPDATE_AFTER - return what is available now and schedule an update on the view so subsequent queries will use newer results
FALSE - schedule a view update before returning to make sure all documents are included
Couchbase Server regularly schedules view updates so results are updated periodically.
Also note that using Stale.FALSE will incur a longer time to return because it has to finish processing the view updates before returning the result.