Search scroll returning no hits (possible bug in 6.2?)

Elastic Stack Elasticsearch
2

Also finding some issues on the ES host (self hosted, simply one node)

[2018-06-13T08:27:32,030][DEBUG][o.e.a.s.TransportSearchScrollAction] [masterdata-node-1] [14332] Failed to execute query phase
org.elasticsearch.transport.RemoteTransportException: [masterdata-node-1][192.168.3.187:9300][indices:data/read/search[phase/query/scroll]]
Caused by: org.elasticsearch.search.SearchContextMissingException: No search context found for id [14332]
	at org.elasticsearch.search.SearchService.findContext(SearchService.java:520) ~[elasticsearch-6.2.3.jar:6.2.3]
	at org.elasticsearch.search.SearchService.executeQueryPhase(SearchService.java:391) ~[elasticsearch-6.2.3.jar:6.2.3]
	at org.elasticsearch.action.search.SearchTransportService$8.messageReceived(SearchTransportService.java:410) ~[elasticsearch-6.2.3.jar:6.2.3]
	at org.elasticsearch.action.search.SearchTransportService$8.messageReceived(SearchTransportService.java:407) ~[elasticsearch-6.2.3.jar:6.2.3]
	at org.elasticsearch.transport.RequestHandlerRegistry.processMessageReceived(RequestHandlerRegistry.java:66) ~[elasticsearch-6.2.3.jar:6.2.3]
	at org.elasticsearch.transport.TransportService$7.doRun(TransportService.java:656) [elasticsearch-6.2.3.jar:6.2.3]
	at org.elasticsearch.common.util.concurrent.ThreadContext$ContextPreservingAbstractRunnable.doRun(ThreadContext.java:672) [elasticsearch-6.2.3.jar:6.2.3]
	at org.elasticsearch.common.util.concurrent.AbstractRunnable.run(AbstractRunnable.java:37) [elasticsearch-6.2.3.jar:6.2.3]
	at org.elasticsearch.common.util.concurrent.TimedRunnable.doRun(TimedRunnable.java:41) [elasticsearch-6.2.3.jar:6.2.3]
	at org.elasticsearch.common.util.concurrent.AbstractRunnable.run(AbstractRunnable.java:37) [elasticsearch-6.2.3.jar:6.2.3]
	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149) [?:1.8.0_171]
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624) [?:1.8.0_171]
	at java.lang.Thread.run(Thread.java:748) [?:1.8.0_171]
[2018-06-13T08:27:32,030][DEBUG][o.e.a.s.TransportSearchScrollAction] [masterdata-node-1] [14333] Failed to execute query phase
org.elasticsearch.transport.RemoteTransportException: [masterdata-node-1][192.168.3.187:9300][indices:data/read/search[phase/query/scroll]]
Caused by: org.elasticsearch.search.SearchContextMissingException: No search context found for id [14333]
	at org.elasticsearch.search.SearchService.findContext(SearchService.java:520) ~[elasticsearch-6.2.3.jar:6.2.3]
	at org.elasticsearch.search.SearchService.executeQueryPhase(SearchService.java:391) ~[elasticsearch-6.2.3.jar:6.2.3]
	at org.elasticsearch.action.search.SearchTransportService$8.messageReceived(SearchTransportService.java:410) ~[elasticsearch-6.2.3.jar:6.2.3]
	at org.elasticsearch.action.search.SearchTransportService$8.messageReceived(SearchTransportService.java:407) ~[elasticsearch-6.2.3.jar:6.2.3]
	at org.elasticsearch.transport.RequestHandlerRegistry.processMessageReceived(RequestHandlerRegistry.java:66) ~[elasticsearch-6.2.3.jar:6.2.3]
	at org.elasticsearch.transport.TransportService$7.doRun(TransportService.java:656) [elasticsearch-6.2.3.jar:6.2.3]
	at org.elasticsearch.common.util.concurrent.ThreadContext$ContextPreservingAbstractRunnable.doRun(ThreadContext.java:672) [elasticsearch-6.2.3.jar:6.2.3]
	at org.elasticsearch.common.util.concurrent.AbstractRunnable.run(AbstractRunnable.java:37) [elasticsearch-6.2.3.jar:6.2.3]
	at org.elasticsearch.common.util.concurrent.TimedRunnable.doRun(TimedRunnable.java:41) [elasticsearch-6.2.3.jar:6.2.3]
	at org.elasticsearch.common.util.concurrent.AbstractRunnable.run(AbstractRunnable.java:37) [elasticsearch-6.2.3.jar:6.2.3]
	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149) [?:1.8.0_171]
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624) [?:1.8.0_171]
	at java.lang.Thread.run(Thread.java:748) [?:1.8.0_171]

Any help/hint would be really appreciated