After debugging found something at kibana logs , thats related to orphan watcher , here the log i found

{"type":"log","@timestamp":"2019-09-04T10:06:54Z","tags":["plugin","debug"],"pid":26052,"message":"Checking Elasticsearch version"}
{"type":"log","@timestamp":"2019-09-04T10:06:55Z","tags":["debug","Sentinl","scheduler"],"pid":26052,"message":"cluster disabled"}
{"type":"log","@timestamp":"2019-09-04T10:06:55Z","tags":["debug","Sentinl","scheduler"],"pid":26052,"message":"reloading watchers..."}
{"type":"log","@timestamp":"2019-09-04T10:06:55Z","tags":["debug","Sentinl","get_elasticsearch_client"],"pid":26052,"message":"auth via Kibana server elasticsearch plugin"}
{"type":"log","@timestamp":"2019-09-04T10:06:55Z","tags":["debug","Sentinl","get_elasticsearch_client"],"pid":26052,"message":"auth via Kibana server elasticsearch plugin"}
{"type":"log","@timestamp":"2019-09-04T10:06:55Z","tags":["debug","Sentinl","get_elasticsearch_client"],"pid":26052,"message":"auth via Kibana server elasticsearch plugin"}
{"type":"log","@timestamp":"2019-09-04T10:06:56Z","tags":["debug","Sentinl","scheduler"],"pid":26052,"message":"deleting orphan watchers: 501e4c10-cd63-11e9-aaa0-a100e45a8f06"}
{"type":"log","@timestamp":"2019-09-04T10:06:56Z","tags":["debug","Sentinl","scheduler"],"pid":26052,"message":"scheduled watcher 501e4c10-cd63-11e9-aaa0-a100e45a8f06, to run every every 2 minutes"}

i just removed sentinl and optimize again , but still issue persist 

Hey @lmangani and @sergibondarenko , could you please respond ?

Remove sentinl plugin from kibana and reconfigure , still get the alerts from orphan watcher
necessary Precaution has been taken by deleting watcher index from elastic search but it re create again once plugin get installed

Trying to delete watcher by using sentinl API , but found error that watcher is not present , dont understand where is the alert came from ?
Here is the response that has been captured

curl  -Ss -XDELETE "http://admin:admin@192.168.1.10:5601/api/sentinl/watcher/501e4c10-cd63-11e9-aaa0-a100e45a8f06?pretty" \
  -H 'kbn-version: 6.5.4'

< --- kibana.log  --->>

{"type":"error","@timestamp":"2019-09-13T05:07:45Z","tags":[],"pid":32614,"level":"error","error":{"message":"Saved object [sentinl-watcher/501e4c10-cd63-11e9-aaa0-a100e45a8f06] not found","name":"Error","stack":"Error: Saved object [sentinl-watcher/501e4c10-cd63-11e9-aaa0-a100e45a8f06] not found\n    at handleESError (/usr/share/kibana/plugins/sentinl/server/lib/handle_es_error.js:29:17)\n    at handler (/usr/share/kibana/plugins/sentinl/server/routes/watcher.js:109:22)\n    at <anonymous>"},"url":{"protocol":null,"slashes":null,"auth":null,"host":null,"port":null,"hostname":null,"hash":null,"search":"?pretty","query":{"pretty":""},"pathname":"/api/sentinl/watcher/501e4c10-cd63-11e9-aaa0-a100e45a8f06","path":"/api/sentinl/watcher/501e4c10-cd63-11e9-aaa0-a100e45a8f06?pretty","href":"/api/sentinl/watcher/501e4c10-cd63-11e9-aaa0-a100e45a8f06?pretty"},"message":"Saved object [sentinl-watcher/501e4c10-cd63-11e9-aaa0-a100e45a8f06] not found"}
{"type":"response","@timestamp":"2019-09-13T05:07:45Z","tags":[],"pid":32614,"method":"delete","statusCode":500,"req":{"url":"/api/sentinl/watcher/501e4c10-cd63-11e9-aaa0-a100e45a8f06?pretty=","method":"delete","headers":{"user-agent":"curl/7.29.0","host":"192.168.1.10:5601","accept":"*/*","kbn-version":"6.5.4"},"remoteAddress":"192.168.1.10","userAgent":"192.168.1.10"},"res":{"statusCode":500,"responseTime":731,"contentLength":9},"message":"DELETE /api/sentinl/watcher/501e4c10-cd63-11e9-aaa0-a100e45a8f06?pretty= 500 731ms - 9.0B"}

Hi!

I got same issue. Did you have any chance to find out where this orphaned watcher is stored?

Thanks,
Jan

@YanekR
you need to delete mapping of sentinl from .kibana index , if you have less priority saved object then just delete it and recreate

still waiting for appropriate response from @sirensolutions Team