Intermittently, when a pipeline uses the "@Grab" notation, it results in the following error: 
java.lang.RuntimeException: Error grabbing Grapes – [unresolved dependency: commons-codec#commons-codec;1.9: java.util.ConcurrentModificationException at java.util.ArrayList$Itr.checkForComodification(ArrayList.java:909)] 

If this is related to GROOVY-7407, perhaps the recommended WorkaroundGroovy7407WrappingGrapeEngine.java could be imported into workflow-cps-global-lib and called the first time a trusted library is loaded (before it can attempt to grab anything)?