Kafka-connector: Some fields in the JSON are being stringified in the topic

Hey all,
I connected a mongo collection with a kafka topic using MongoDB Atlas Source in confluent cloud.
I’m using JSON as the output format, however, when fetching messages from the topic, some fields in the JSON are being stringified and not being passed as an object. See attached screenshot:

The message from the topic (see the _id and engagement.history fields) :

Would love some help with understanding how to fix it.
Thanks!

Regarding the above issue this is the doc in the collection:
image