Brett Meyer commented on an issue
Hibernate ORM / Bug HHH-8356
java.util.ConcurrentModificationException in org.hibernate.collection.AbstractPersistentCollection
A java.util.ConcurrentModificationException happened in the following for loop. I think java.util.ConcurrentModificationException should not happen in iteration when an item is removed but iteration should be thread-safe.

            for (final TargetRun targetRun : targetRuns) {
                final MetaRun metaRun = targetRun.getMetaRun();
       ...