Save Conflict: Your changes conflict with those made concurrently by another user. If you want your changes to be applied, click back in your Web browser, refresh the page, and resubmit your changes

Issue: Save Conflict. Your changes conflict with those made concurrently by another user. If you want your changes to be applied, click back in your Web browser, refresh the page, and resubmit your changes.

The Cause of the Issue: When you are attempting to update the SharePoint list item, which has been changed by another user since you opened it.

Cases: 

1) Mostly this problem will occur during the update of a SharePoint List Item in Event Receivers and Workflows, which are running whenever the item changes.

Example: I have a SharePoint workflow on custom list, which is running whenever the item changes. In my workflow code I’m trying to set the value to one of the custom fields, after setting the value to the custom field, I update the list item. Here the item was changed and the workflow again triggered on the same. We can solve this type of problem by disables firing event receiver or workflow while updating item.

2) Sometimes, it is necessary to update the same list item in our code parallel. At that time also this error will occur.

Solution: Instead of performing operations on the item which will get updated by another process, get the same item from SharePoint list based on Unique ID by using “SPList.GetItemByUniqueId” method.