Database
db={transaction:[{/** doc 1*/_id:"doc 1 is okay",TransactionStatus:[{StatusType:2},{StatusType:1}]},{/** doc 2*/_id:"doc 2 is okay",TransactionStatus:{StatusType:[2,1]}},{/** doc 3 - this one has an issue*/_id:"doc 3 causes the error",TransactionStatus:{StatusType:1}}]}
Query
db.transaction.find({$expr:{"$ne":[{"$type":"$TransactionStatus.StatusType"},"array"]}})