An error occurred during the backup (id=1)

I do an automatic remote server backup of all accounts

what is the solution to this problem?

Code:

User admin has been backed up. <2:05:02>
User xxxxx has been backed up. <2:10:50>
ftp_upload.php exit code: 28
ftp_upload.php output: curl: (28) FTP response timeout
curl retu code: 28
<2:42:28>
User xxxxx has been backed up. <2:42:29>
User xxxxx has been backed up. <2:42:31>
User xxxxx has been backed up. <2:42:33>
User xxxxx has been backed up. <2:53:33>
ftp_upload.php exit code: 28
ftp_upload.php output: curl: (28) FTP response timeout
curl retu code: 28
<4:00:35>
User xxxxx has been backed up. <4:02:47>

Although a backup error has occurred, the upload of valid backups would have still been attempted to ftps://xxxxx /2017-11-01/2017-11-22 <4:08:46>

FTP has lost connection, can be a network problem, happens to me sometimes

always the same problem. no solution?