Hi,

We've been running into this issue lately and I think the below line that’s throwing the exception: 
https://github.com/jenkinsci/s3-plugin/blob/master/src/main/java/hudson/plugins/s3/S3Profile.java#L240

Any ideas?

java.util.ConcurrentModificationExceptionjava.util.ConcurrentModificationException at java.util.ArrayList$Itr.checkForComodification(ArrayList.java:909) at java.util.ArrayList$Itr.next(ArrayList.java:859) at hudson.plugins.s3.S3Profile.downloadAll(S3Profile.java:240) at hudson.plugins.s3.S3CopyArtifact.perform(S3CopyArtifact.java:270) at hudson.plugins.s3.S3CopyArtifact.perform(S3CopyArtifact.java:242) at org.jenkinsci.plugins.workflow.steps.CoreStep$Execution.run(CoreStep.java:80) at org.jenkinsci.plugins.workflow.steps.CoreStep$Execution.run(CoreStep.java:67) at org.jenkinsci.plugins.workflow.steps.SynchronousNonBlockingStepExecution.lambda$start$0(SynchronousNonBlockingStepExecution.java:47) at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511) at java.util.concurrent.FutureTask.run(FutureTask.java:266) at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149) at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624) at java.lang.Thread.run(Thread.java:748)Finished: FAILURE