Hi, I am experiencing the same problem as described in this topic. To answer Alexanders question, the backup actually does complete and is written to that folder location so the execution user must have the necessary permission to that destination folder.
As can be seen here the line before the "Failed to backup" entry says "database backup successfully completed." and the backup file can indeed be found in the destination directory.
12/10/2017 18:58 "DatabaseName" database backup successfully completed. Backup type: "Full"
12/10/2017 18:58 Failed to backup "DatabaseName" database with "Full" backup type: Could not find file 'D:\Database Backups\inpex1.buildmehost.com\DatabaseName201710121858.bak'.