New Post: Error after UpdateListItems - The file has been modified by SHAREPOINT\system on 18 Feb 2014 12:00:13 -080

I have a document library (sharepoint server 2013 + sharepoint designer 2013), which can be uploaded documents. I created a column (AssignedCustomers) with multiple choice (checkboxs) for customers so that when a document gets uploaded, user can pick up the customers for the document. but the column [AssignedCustomers) is populated dynamically from another list (I also use spservice to query another a list) and populate the checkboxlist by using Jquery. I put them in document.ready of editform.aspx:

1. using spservice query another list get available customers;
2. manipulate checkbox lists by replacing default values with the values from step 1 - using JQuery on client side on DOM/HTML;
3. update the list by using spervice(UpdateListItems) to update the list for the document just uploaded with the values from step 1;
4. in PreSaveAction, using spservice (UpdateListItems) to update the list based on the selection on checkboxlist.
   

the document finally uploaded and the AssignedCustomers column can be assigned correct values with no issues. the only thing is the error ""The file has been modified by SHAREPOINT\system on 18 Feb 2014 12:00:13 -0800" when click "Save" button will appear on the bottom of editform or a popup window. if I click "cancel" button or close the popup window, the document can still be uploaded successfully.
so I am wondering how to disable this error message when calling spservice or there is another way doing that.

Thanks for looking at this post and hopefully there are helps here.