Update: There are two issues. One is being unable to write a JSON object using the set entity property. The other is that you cannot retrieve the entity property as a JSON object, it is returned as a string see AUT-1696.
We are attempting to copy an entity property from a parent issue to a subtask. Everything is working as expected; however, when we use the Set issue property it writes the values as a string and adds quotation marks around the json we are adding, which makes the JSON invalid.
Is this a bug or is there some work around?
The automation rule we have created is:

The result is this
