Getting java.util.ConcurrentModificationException in production logs, and  looks like it's being occurred by OOTB rule.

Any idea when this exception is getting triggered ?

PRPC:7.1.8

Exception;java.util.ConcurrentModificationException; at java.util.HashMap$HashIterator.nextNode(HashMap.java:1429); at java.util.HashMap$ValueIterator.next(HashMap.java:1458); at com.pega.pegarules.data.internal.clipboard.ClipboardPageImpl.clearMessages(ClipboardPageImpl.java:3869); at com.pegarules.generated.activity.ra_action_pzdogridaction_84f3e7348d7bf2bad1ec28065f8afa87.step1_circum0(ra_action_pzdogridaction_84f3e7348d7bf2bad1ec28065f8afa87.java:367); at com.pegarules.generated.activity.ra_action_pzdogridaction_84f3e7348d7bf2bad1ec28065f8afa87.perform(ra_action_pzdogridaction_84f3e7348d7bf2bad1ec28065f8afa87.java:69); at com.pega.pegarules.session.internal.mgmt.Executable.doActivity(Executable.java:3500); at com.pegarules.generated.activity.ra_action_reloadsection_da485226efeafad250cd6b7ad21ded26.step5_circum0(ra_action_reloadsection_da485226efeafad250cd6b7ad21ded26.java:734); at com.pegarules.generated.activity.ra_action_reloadsection_da485226efeafad250cd6b7ad21ded26.perform(ra_action_reloadsection_da485226efeafad250cd6b7ad21ded26.java:137); at com.pega.pegarules.session.internal.mgmt.Executable.doActivity(Executable.java:3500); at com.pega.pegarules.session.internal.mgmt.base.ThreadRunner.runActivitiesAlt(ThreadRunner.java:646); at com.pega.pegarules.session.internal.mgmt.PRThreadImpl.runActivitiesAlt(PRThreadImpl.java:461); at com.pega.pegarules.session.internal.engineinterface.service.HttpAPI.runActivities(HttpAPI.java:3322); at com.pega.pegarules.session.external.engineinterface.service.EngineAPI.processRequestInner(EngineAPI.java:385); at sun.reflect.GeneratedMethodAccessor50.invoke(Unknown Source); at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43); at java.lang.reflect.Method.invoke(Method.java:483); at com.pega.pegarules.session.internal.PRSessionProviderImpl.performTargetActionWithLock(PRSessionProviderImpl.java:1270); at com.pega.pegarules.session.internal.PRSessionProviderImpl.doWithRequestorLocked(PRSessionProviderImpl.java:1008); at com.pega.pegarules.session.internal.PRSessionProviderImpl.doWithRequestorLocked(PRSessionProviderImpl.java:841); at com.pega.pegarules.session.external.engineinterface.service.EngineAPI.processRequest(EngineAPI.java:331); at com.pega.pegarules.session.internal.engineinterface.service.HttpAPI.invoke(HttpAPI.java:850); at com.pega.pegarules.session.internal.engineinterface.etier.impl.EngineImpl._invokeEngine_privact(EngineImpl.java:315); at com.pega.pegarules.session.internal.engineinterface.etier.impl.EngineImpl.invokeEngine(EngineImpl.java:263); at com.pega.pegarules.session.internal.engineinterface.etier.impl.EngineImpl.invokeEngine(EngineImpl.java:240); at com.pega.pegarules.priv.context.JNDIEnvironment.invokeEngineInner(JNDIEnvironment.java:278); at com.pega.pegarules.priv.context.JNDIEnvironment.invokeEngine(JNDIEnvironment.java:223); at com.pega.pegarules.web.impl.WebStandardImpl.makeEtierRequest(WebStandardImpl.java:574); at com.pega.pegarules.web.impl.WebStandardImpl.doPost(WebStandardImpl.java:374); at sun.reflect.GeneratedMethodAccessor49.invoke(Unknown Source); at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43); at java.lang.reflect.Method.invoke(Method.java:483); at com.pega.pegarules.internal.bootstrap.PRBootstrap.invokeMethod(PRBootstrap.java:367); at com.pega.pegarules.internal.bootstrap.PRBootstrap.invokeMethodPropagatingThrowable(PRBootstrap.java:408); at com.pega.pegarules.boot.internal.extbridge.AppServerBridgeToPega.invokeMethodPropagatingThrowable(AppServerBridgeToPega.java:223); at com.pega.pegarules.boot.internal.extbridge.AppServerBridgeToPega.invokeMethod(AppServerBridgeToPega.java:272); at com.pega.pegarules.internal.web.servlet.WebStandardBoot.doPost(WebStandardBoot.java:121); at javax.servlet.http.HttpServlet.service(HttpServlet.java:754); at javax.servlet.http.HttpServlet.service(HttpServlet.java:847); at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:295); at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:214); at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:231); at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:149); at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:420); at org.jboss.as.web.session.ClusteredSessionValve.handleRequest(ClusteredSessionValve.java:134); at org.jboss.as.web.session.ClusteredSessionValve.invoke(ClusteredSessionValve.java:99); at org.jboss.as.web.session.JvmRouteValve.invoke(JvmRouteValve.java:92); at org.jboss.as.web.session.LockingValve.invoke(LockingValve.java:64); at org.jboss.web.rewrite.RewriteValve.invoke(RewriteValve.java:272); at org.jboss.as.web.security.SecurityContextAssociationValve.invoke(SecurityContextAssociationValve.java:169); at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:145); at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:97); at org.jboss.web.rewrite.RewriteValve.invoke(RewriteValve.java:466); at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:102); at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:344); at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:856); at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:653); at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:926); at java.lang.Thread.run(Thread.java:745);