ServiceNow strongly recommends do not delete sys_update_xml entries. As this action may lead to several issues on the instance it is necessary to track deletions from this table. Deletions from tables with a sys_ prefix are not audited by default.
Enable auditing for update sets by adding the sys_update_xml table to the glide.ui.audit_deleted_tables property. This will enable auditing of deletions from Update sets.
Time to fix