Deleted documents in Elastic Search for Magento

I'm using Elastic Search with Magento 2.1.7 and frequently I encounter missing (deleted) documents after the index is completed; has anyone encountered this before ?

Hi,

How is Magento implementing with Elasticsearch here?
What do you mean by after the index is completed- what action is completed?
Please share as much as you can to get breadth of where the issue could be.