not sure about the 18:54 error opening a file.
but the 19:16 list of messages usually happens when the server was in the middle of a backup and the client goes offline “Client Celebrado Server went offline”… for instance, in my case I noticed this issue when some workstations went to hibernation a few hours after the user locked it. Also there is a delay between the time the client shutdowns and the urbackup server reports the issue (probably because it retries before timing out).
to fix it:
schedule your backups early enough before your workstations start hibernating… for instance if it usually takes 3h to complete the backup. set your hibenation to 4h and schedule your backup around 5pm.