ConcurrentModificationException #159

sometimes I get an exception

java.util.ConcurrentModificationException
at java.util.ArrayList$ArrayListSpliterator.forEachRemaining(ArrayList.java:1388)
at java.util.stream.AbstractPipeline.copyInto(AbstractPipeline.java:481)
at java.util.stream.AbstractPipeline.wrapAndCopyInto(AbstractPipeline.java:471)
at java.util.stream.ForEachOps$ForEachOp.evaluateSequential(ForEachOps.java:151)
at java.util.stream.ForEachOps$ForEachOp$OfRef.evaluateSequential(ForEachOps.java:174)
at java.util.stream.AbstractPipeline.evaluate(AbstractPipeline.java:234)
at java.util.stream.ReferencePipeline.forEach(ReferencePipeline.java:418)
at com.aventstack.extentreports.ReportStatusStats.updateEventsCount(ReportStatusStats.java:394)
at com.aventstack.extentreports.ReportStatusStats.updateEventsCount(ReportStatusStats.java:398)
at com.aventstack.extentreports.ReportStatusStats.addTestForStatusStatsUpdate(ReportStatusStats.java:370)
at java.util.ArrayList.forEach(ArrayList.java:1257)
at com.aventstack.extentreports.ReportStatusStats.refreshStats(ReportStatusStats.java:366)
at com.aventstack.extentreports.ReportStatusStats.refresh(ReportStatusStats.java:65)
at com.aventstack.extentreports.ReportObservable.refreshReportStats(ReportObservable.java:279)
at com.aventstack.extentreports.ReportObservable.refreshReportEntities(ReportObservable.java:271)
at com.aventstack.extentreports.ReportObservable.generateRecentStatus(ReportObservable.java:464)
at com.aventstack.extentreports.ExtentReports.generateRecentStatus(ExtentReports.java:1)
at com.aventstack.extentreports.ReportObservable.flush(ReportObservable.java:423)
at com.aventstack.extentreports.ExtentReports.flush(ExtentReports.java:290)
at infakt.utilities.ExtentTestManager.logInfo(ExtentTestManager.java:34)
at infakt.utilities.ExpectedTitle.waitForTitleContains(ExpectedTitle.java:34)

logInfo looks like this
public static void logInfo(String text) { getEndNode().log(Status.INFO, text); ExtentManager.getInstance().flush(); }

version 4.1.5
I run tests in parallel on 4 threads