title: mongoDB updateOne not updating a record
body: <p>I am trying to update a record in mongoDB using updateOne, the un updating record is in array, and all fields are updating except one field which is <strong>country</strong>, I have tried to update it using MongoChef (a GUI of MongoDB for linux), but it doesn't work, also <strong>If I update one the Document using Edit in GUI then that record is ready to update after that</strong>.</p>
  
  <p>I have tried with the following query in MongoChef</p>
  
  <pre><code>db.institutions.updateOne({
      "campus": { "$elemMatch": { "_id": ObjectId("578500ef87e4c326183e520e")} },
      "_id": ObjectId("57f25706762c06cb7d9422fc") 
      },
      {
      "$set" : { "campus.$.country" : "SS1"
      }
  });
  </code></pre>
  
  <p>Only country field is not updating If I update any other field it works fine.</p>
  
  <p>The document structure is listed under</p>
  
  <pre><code>{ 
      "_id" : ObjectId("57f26824762c06cb7d982e37"), 
      "campus" : [
          {
              "_id" : ObjectId("578500ee87e4c326183e5201"), 
              "country" : "GB", 
              "coreId" : NumberInt(1), 
              "city" : "Norwich", 
          }
      ]
  }
  </code></pre>
  
  <p>Thanks in advance any help is appreciatiable</p>