Logstash stopped processing because of an error: (SystemExit) exit

Hello World!

I'm Running Logstash on Docker | Logstash Reference [6.8] | Elastic and getting following error:

logstash    | Sending Logstash logs to /usr/share/logstash/logs which is now configured via log4j2.properties
logstash    | [2019-08-15T20:50:25,185][INFO ][logstash.configmanagement.bootstrapcheck] Using Elasticsearch as config store {:pipeline_id=>["gelf", "nre", "upsertDome", "upsertMaid", "upsertMinion"], :poll_interval=>"5000000000ns"}
logstash    | [2019-08-15T20:50:26,012][INFO ][logstash.licensechecker.licensereader] Elasticsearch pool URLs updated {:changes=>{:removed=>[], :added=>[https://elastic:xxxxxx@localhost:9200/]}}
logstash    | [2019-08-15T20:50:26,323][WARN ][logstash.licensechecker.licensereader] Attempted to resurrect connection to dead ES instance, but got an error. {:url=>"https://elastic:xxxxxx@localhost:9200/", :error_type=>LogStash::Outputs::ElasticSearch::HttpClient::Pool::HostUnreachableError, :error=>"Elasticsearch Unreachable: [https://elastic:xxxxxx@localhost:9200/][Manticore::SocketException] Connection refused (Connection refused)"}
logstash    | [2019-08-15T20:50:26,385][WARN ][logstash.licensechecker.licensereader] Marking url as dead. Last error: [LogStash::Outputs::ElasticSearch::HttpClient::Pool::HostUnreachableError] Elasticsearch Unreachable: [https://elastic:xxxxxx@localhost:9200/][Manticore::SocketException] Connection refused (Connection refused) {:url=>https://elastic:xxxxxx@localhost:9200/, :error_message=>"Elasticsearch Unreachable: [https://elastic:xxxxxx@localhost:9200/][Manticore::SocketException] Connection refused (Connection refused)", :error_class=>"LogStash::Outputs::ElasticSearch::HttpClient::Pool::HostUnreachableError"}
logstash    | [2019-08-15T20:50:26,398][ERROR][logstash.licensechecker.licensereader] Unable to retrieve license information from license server {:message=>"Elasticsearch Unreachable: [https://elastic:xxxxxx@localhost:9200/][Manticore::SocketException] Connection refused (Connection refused)"}
logstash    | [2019-08-15T20:50:26,585][ERROR][logstash.configmanagement.elasticsearchsource] Failed to fetch X-Pack information from Elasticsearch. This is likely due to failure to reach a live Elasticsearch cluster.
logstash    | [2019-08-15T20:50:26,598][FATAL][logstash.runner          ] An unexpected error occurred! {:error=>#<LogStash::LicenseChecker::LicenseError: Failed to fetch X-Pack information from Elasticsearch. This is likely due to failure to reach a live Elasticsearch cluster.>, :backtrace=>["/usr/share/logstash/x-pack/lib/license_checker/licensed.rb:67:in `with_license_check'", "/usr/share/logstash/x-pack/lib/config_management/elasticsearch_source.rb:46:in `initialize'", "/usr/share/logstash/x-pack/lib/config_management/hooks.rb:41:in `after_bootstrap_checks'", "org/logstash/execution/EventDispatcherExt.java:71:in `execute'", "/usr/share/logstash/logstash-core/lib/logstash/runner.rb:304:in `execute'", "/usr/share/logstash/vendor/bundle/jruby/2.5.0/gems/clamp-0.6.5/lib/clamp/command.rb:67:in `run'", "/usr/share/logstash/logstash-core/lib/logstash/runner.rb:237:in `run'", "/usr/share/logstash/vendor/bundle/jruby/2.5.0/gems/clamp-0.6.5/lib/clamp/command.rb:132:in `run'", "/usr/share/logstash/lib/bootstrap/environment.rb:73:in `<main>'"]}
logstash    | [2019-08-15T20:50:26,612][ERROR][org.logstash.Logstash    ] java.lang.IllegalStateException: Logstash stopped processing because of an error: (SystemExit) exit

there is no error if I'm using logstash 6.8.0 (w/ same configuration), yet error seems to appear only if I use logstash 6.8.1 or 6.8.2.

Please advise.