Database
[{"_id":{"$oid":"632a11c91f786f7d86d7633a"},"List":[{"Name":"WithError","Error":"duplicate"},{"Name":"WithOutError"}]}]
Query
db.collection.update({},[{"$set":{"List":{$map:{input:"$List",as:"element",in:{$cond:{if:{"$and":[{$toBool:"$$element.Error"},{$eq:["string",{$type:"$$element.Error"}]}]},then:{Name:"$$element.Name",Error:["$$element.Error"]},else:"$$element"}}}}}}])