Use CSOM to update project's custom fields

Hi, I have a problem when updating a project using CSOM (on Project Server 2013). I cannot use PSI because I need to move to Project Online in the near future. My code looks like this:

            DraftProject draftProject = onlineProject.CheckOut();            draftProject.SetCustomFieldValue("Project Number", "111");            draftProject.Name = "123";            draftProject.Description = "aab";            //draftProject["ProjectNumber"] = "111";            var job = draftProject.Publish(true);

Note I'm updating the name, the description, and a custom field called Project Number. Now the name is successfully updated. But neither the description nor the custom field is updated, and the service doesn't return any error. Why does the update partially succeeded?

Can someone help? Thanks.

Sining Oh Blue Star