请尝试删除版本历史记录代码，并检查其是否有效.

Please try to remove the version history code and check if it works.

或者我们可以先新建项目，然后根据版本历史记录更新列表项目(分为两个步骤).

Or we can new the item firstly, then update the list item basic on the version history(split two steps).

或者尝试使用以下实用程序方法来简化项目的重新加载.

Or try to use the following utility method to ease the reloading of items.

public static SPListItem ReloadListItem(SPListItem item)
{
    if (item == null)
        return null;
 
    return item.ParentList.GetItemByUniqueId(item.UniqueId);
}

更多信息在这里:

https://adrianhenke.wordpress.com/2010/08/20/sharepoint-error-save-conflict-your-changes-conflict-with-those-made-concurrently-by-other-user/

***的问候，

丹尼斯