Working transaction for comparison:
(000943)23/03/2021 23:58:07 - (not logged in) (1.2.3.4)> 331 Password required for the ftp username
(000943)23/03/2021 23:58:07 - (not logged in) (1.2.3.4)> PASS ******
(000943)23/03/2021 23:58:07 - the ftp username (1.2.3.4)> 230 Logged on
(000943)23/03/2021 23:58:07 - the ftp username (1.2.3.4)> TYPE I
(000943)23/03/2021 23:58:07 - the ftp username (1.2.3.4)> 200 Type set to I
(000943)23/03/2021 23:58:07 - the ftp username (1.2.3.4)> PWD
(000943)23/03/2021 23:58:07 - the ftp username (1.2.3.4)> 257 "/" is current directory.
(000943)23/03/2021 23:58:07 - the ftp username (1.2.3.4)> PASV
(000943)23/03/2021 23:58:07 - the ftp username (1.2.3.4)> 227 Entering Passive Mode (192,168,123,123,243,60)
(000943)23/03/2021 23:58:07 - the ftp username (1.2.3.4)> STOR /backups/customer/backup_dbsave_customer_13.2.1.27_20210323235508.tar.tmp
(000943)23/03/2021 23:58:07 - the ftp username (1.2.3.4)> 150 Opening data channel for file upload to server of "/backups/customer/backup_dbsave_customer_13.2.1.27_20210323235508.tar.tmp"
(000943)23/03/2021 23:58:45 - the ftp username (1.2.3.4)> 226 Successfully transferred "/backups/customer/backup_dbsave_customer_13.2.1.27_20210323235508.tar.tmp"
(000943)23/03/2021 23:58:45 - the ftp username (1.2.3.4)> RNFR /backups/customer/backup_dbsave_customer_13.2.1.27_20210323235508.tar.tmp
(000943)23/03/2021 23:58:45 - the ftp username (1.2.3.4)> 350 File exists, ready for destination name.
(000943)23/03/2021 23:58:45 - the ftp username (1.2.3.4)> RNTO /backups/customer/backup_dbsave_customer_13.2.1.27_20210323235508.tar
(000943)23/03/2021 23:58:45 - the ftp username (1.2.3.4)> 250 file renamed successfully
(000943)23/03/2021 23:58:45 - the ftp username (1.2.3.4)> QUIT
(000943)23/03/2021 23:58:45 - the ftp username (1.2.3.4)> 221 Goodbye
What's going on with that "restart" command? Is the connection timing out? No timestamps in your log, hard to tell.
Try creating a scheduled FTP export of one of the smaller forms, see if that works.