An UnsupportedOperationException is thrown from DomainObjectReader.handleArrayNode(DomainObjectReader.java:272) in case when json update (new) object node contains an array property that was undefined in the source (old) object
That should be in place now. I've added a couple more advanced fixes that sort of relate to the same problem. We're now skipping merging of null values completely and also back out on a potential non-collection source value.
Thanks for the PR. Feel free to give the snapshots a try