https://blog.it-kb.ru/2019/04/05/sharepoint-2013-farm-powershell-full-backup-spfarm-exception-an-update-conflict-has-occurred-spupdatedconcurrencyexception/
Попытка резервного копирования фермы SharePoint 2013 приводит к исключению Backup-SPFarm : An update conflict has occurred, and you must re-try this action …SPUpdatedConcurrencyException