(from osdn.net/users/k-uno)
[検索]ボタンを押下したあと、Firefox 52.0では正常完了しますが、Internet Explorer 11で同じ操作（検索文字列、ログイン状態も同じ）をすると、後述するログの通りTimeoutが発生して検索結果が表示されません。Timeoutの確率は100％です。
考えられる原因と回避策を教えて頂きたいですが、先ずは当該ログのみ送付致します。
------------------------------------ 以下、fess.log抜粋（必要に応じて前後も添付します） ------------------------------------
= = = = = = = = = =/ [03m01s027ms] #55ca1cba
ElasticsearchTimeoutException[java.util.concurrent.TimeoutException: Timeout waiting for task.]; nested: TimeoutException[Timeout waiting for task.];
at org.elasticsearch.action.support.AdapterActionFuture.actionGet(AdapterActionFuture.java:70)
at org.elasticsearch.action.support.AdapterActionFuture.actionGet(AdapterActionFuture.java:62)
at org.elasticsearch.action.support.AdapterActionFuture.actionGet(AdapterActionFuture.java:52)
at org.codelibs.fess.es.log.allcommon.EsAbstractBehavior.delegateInsert(EsAbstractBehavior.java:270)
at org.dbflute.bhv.AbstractBehaviorWritable.doInsert(AbstractBehaviorWritable.java:87)
at org.codelibs.fess.es.log.bsbhv.BsUserInfoBhv.insert(BsUserInfoBhv.java:178)
at org.codelibs.fess.helper.SearchLogHelper.lambda$updateUserInfo$1188(SearchLogHelper.java:189)
at org.dbflute.optional.BaseOptional.lambda$static$1(BaseOptional.java:43)
at org.codelibs.fess.helper.SearchLogHelper.updateUserInfo(SearchLogHelper.java:184)
at org.codelibs.fess.helper.UserInfoHelper.updateUserSessionId(UserInfoHelper.java:80)
at org.codelibs.fess.helper.UserInfoHelper.getUserCode(UserInfoHelper.java:70)
at org.codelibs.fess.helper.SearchLogHelper.addSearchLog(SearchLogHelper.java:85)
at org.codelibs.fess.app.service.SearchService.search(SearchService.java:160)
at org.codelibs.fess.app.web.search.SearchAction.doSearch(SearchAction.java:128)
at org.codelibs.fess.app.web.search.SearchAction.search(SearchAction.java:82)
at org.codelibs.fess.app.web.search.SearchAction.index(SearchAction.java:69)
at sun.reflect.GeneratedMethodAccessor182.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.lang.reflect.Method.invoke(Unknown Source)
at org.lastaflute.web.ruts.GodHandableAction.invokeExecuteMethod(GodHandableAction.java:335)
at org.lastaflute.web.ruts.GodHandableAction.actuallyExecute(GodHandableAction.java:306)
at org.lastaflute.web.ruts.GodHandableAction.doExecute(GodHandableAction.java:146)
at org.lastaflute.web.ruts.GodHandableAction.lambda$transactionalExecute$0(GodHandableAction.java:137)
at org.lastaflute.db.jta.stage.JTATransactionStage.doPerform(JTATransactionStage.java:71)
at org.lastaflute.db.jta.stage.JTATransactionStage.lambda$requiresNew$1(JTATransactionStage.java:59)
at org.lastaflute.di.tx.adapter.JTATransactionManagerAdapter.requiresNew(JTATransactionManagerAdapter.java:73)
at org.lastaflute.db.jta.stage.JTATransactionStage.requiresNew(JTATransactionStage.java:58)
at org.lastaflute.db.jta.stage.JTATransactionStage.selectable(JTATransactionStage.java:100)
at org.lastaflute.web.ruts.GodHandableAction.transactionalExecute(GodHandableAction.java:136)
at org.lastaflute.web.ruts.GodHandableAction.execute(GodHandableAction.java:117)
at org.lastaflute.web.ruts.ActionRequestProcessor.performAction(ActionRequestProcessor.java:194)
at org.lastaflute.web.ruts.ActionRequestProcessor.fire(ActionRequestProcessor.java:130)
at org.lastaflute.web.ruts.ActionRequestProcessor.process(ActionRequestProcessor.java:101)
at org.lastaflute.web.servlet.filter.RequestRoutingFilter.processAction(RequestRoutingFilter.java:248)
at org.lastaflute.web.servlet.filter.RequestRoutingFilter.routingToAction(RequestRoutingFilter.java:200)
at org.lastaflute.web.servlet.filter.RequestRoutingFilter.lambda$createActionPathHandler$0(RequestRoutingFilter.java:173)
at org.lastaflute.web.path.ActionPathResolver.actuallyHandleActionPath(ActionPathResolver.java:269)
at org.lastaflute.web.path.ActionPathResolver.doHandleActionPath(ActionPathResolver.java:144)
at org.lastaflute.web.path.ActionPathResolver.handleActionPath(ActionPathResolver.java:111)
at org.lastaflute.web.servlet.filter.RequestRoutingFilter.doFilter(RequestRoutingFilter.java:115)
at org.lastaflute.web.servlet.filter.LastaToActionFilter.viaEmbeddedFilter(LastaToActionFilter.java:152)
at org.lastaflute.web.servlet.filter.LastaToActionFilter.viaInsideHookDeque(LastaToActionFilter.java:143)
at org.lastaflute.web.servlet.filter.LastaToActionFilter.viaInsideHook(LastaToActionFilter.java:127)
at org.lastaflute.web.servlet.filter.LastaToActionFilter.doFilter(LastaToActionFilter.java:119)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:192)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:165)
at org.lastaflute.web.servlet.filter.LastaShowbaseFilter.toNextChain(LastaShowbaseFilter.java:165)
at org.lastaflute.web.servlet.filter.LastaShowbaseFilter.lambda$viaEmbeddedFilter$1(LastaShowbaseFilter.java:144)
at org.lastaflute.web.servlet.filter.RequestLoggingFilter.actuallyFilter(RequestLoggingFilter.java:212)
at org.lastaflute.web.servlet.filter.RequestLoggingFilter.doFilter(RequestLoggingFilter.java:197)
at org.lastaflute.web.servlet.filter.LastaShowbaseFilter.viaEmbeddedFilter(LastaShowbaseFilter.java:142)
at org.lastaflute.web.servlet.filter.LastaShowbaseFilter.viaOutsideHookDeque(LastaShowbaseFilter.java:133)
at org.lastaflute.web.servlet.filter.LastaShowbaseFilter.viaOutsideHook(LastaShowbaseFilter.java:117)
at org.lastaflute.web.servlet.filter.LastaShowbaseFilter.doFilter(LastaShowbaseFilter.java:109)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:192)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:165)
at org.codelibs.fess.filter.WebApiFilter.doFilter(WebApiFilter.java:51)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:192)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:165)
at org.lastaflute.web.servlet.filter.LastaPrepareFilter.toNextFilter(LastaPrepareFilter.java:279)
at org.lastaflute.web.servlet.filter.LastaPrepareFilter.viaHotdeploy(LastaPrepareFilter.java:242)
at org.lastaflute.web.servlet.filter.LastaPrepareFilter.viaLastaDiContext(LastaPrepareFilter.java:229)
at org.lastaflute.web.servlet.filter.LastaPrepareFilter.doFilter(LastaPrepareFilter.java:202)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:192)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:165)
at org.codelibs.fess.filter.EncodingFilter.doFilter(EncodingFilter.java:119)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:192)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:165)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:198)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:108)
at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:472)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:140)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:79)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:87)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:349)
at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:784)
at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:66)
at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:802)
at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1410)
at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49)
at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
at java.lang.Thread.run(Unknown Source)
Caused by: java.util.concurrent.TimeoutException: Timeout waiting for task.
at org.elasticsearch.common.util.concurrent.BaseFuture$Sync.get(BaseFuture.java:232)
at org.elasticsearch.common.util.concurrent.BaseFuture.get(BaseFuture.java:67)
at org.elasticsearch.action.support.AdapterActionFuture.actionGet(AdapterActionFuture.java:68)
… 83 more
2017-06-07 17:06:05,704 [http-nio-80-exec-13] DEBUG {FAILURE}: /search/
*Read the exception message!