Unrecoverable readfile error captured, backup will not complete.

Hello Friends

I have a clustered file share of 45 tb in size when I run the full backup it only saves 15 Tb or less,

the backup ends without apparent errors, but when I check the log ,I see the following error messages

91579: save: Unrecoverable readfile error captured, backup will not complete.

and in several files the following  for example:

5191:save: File S:\HOMEUSVDI$\1465432\Documents\TAREA\CARPETA\2020\09.SEPTIEMBRE\INBOX\semana 22-28\Saludos.msg could not be opened and was not backed up. (No such file or directory)

another error is that it does not let me navigate over all the backed up folders

I have 4 savestreams configured.

I HOPE someone can help me