To be honest this seems to be an issue in Serilog which is still open.
The Elasticsearch has been upgraded from 5.2.x to 6.5.2.
Suppose the existing index followed the naming pattern log-abc-2008.12. Now if I delete this index and then try to run the serilog, something strange happens. The index is not created. It is able to create log-ABCD-2018.
Is there some trace of old indices somewhere hidden in Elasticsearch or kibana. I will like to remove it.