Experimental deepcopy of map objects in c++ was added in c71a02e, but my guess is that refactoring has meant this has gotten out of date (or at least it is not well tested).
So, going to disable in python bindings for now and keep this ticket open to flag returning to getting this solid in future releases.
See also #946
disable deepcopy in python bindings until this is more solid - refs #…
closing, plan outlined for this at #2081
remove unused and broken deepcopy support to be replaced in #2081 - r…
…efs #1390 and #946