Error 550 no such file or directory

I cannot make any backup (databases nor files). Each backup fails on this type of message :
"Sending backup “blablabla” to FTP destination “blablabla”
"Uploading local “blablabla” in remote “” in folder “/”
"destination error :could not delete ; no such file or directory (550)

Any hint ?

Hi UNITIC_Francis_Lopez,

To investigate this case we need more details. Could you please provide us with the Advanced Log, here are more details on how to do it

Please let us know when the log will be sent. Also, please provide us with your Application ID (“Help” > “About”) to identify the log.

Sorry for the insconvenience.