Yup, thats specifically why we shouldn't be reimplementing close and having the same errors 

In this case its cloning options which are safe, the error is only when we persist modified objects, I think the fix is different though, since we cant do a json clone on the original objects since they may contain binary objects, I think we should leave the original clone as is, and strip (+1 warn) unsupported things from the documents as they are stored