Full backup to ftp

Hi,
we have the following problem: we back up to amazon and to our ftp server. The full backup to the ftp server does not work, while the Diff copies are made without any problems. Also, full backup files appear on ftp and each new file has a slightly larger size, as it probably should be. But these files do not appear in the list of available backups to restore.
This is what appears in the logs (names and addresses changed):

9/13/2022 10:20 AM Backup of “DATA” successfully compressed to “(DATA202209130300.zip : 36.405GB)”.
9/13/2022 10:20 AM Connecting to “FTP” destination “ftp”.
9/13/2022 10:20 AM The current destination folder is “backups”.
9/13/2022 10:20 AM Sending backup of “system” to “FTP” destination “backups”.
9/13/2022 10:20 AM Uploading local “DATA202209130300.zip” to remote “DATA202209130300.zip” in folder “backups”.
9/13/2022 1:23 PM Destination error: Cannot send command to the server because the response for previous one was not received.
9/13/2022 1:23 PM Destination error: ${https://sqlbackupandftp.com/kb?id=DST-2%3A1103%230|#[DST-2:1103#0]} Failed to upload “D:\Backups\SQLBackupAndFTP\SBF\281c292e-89ab-4a0a-9c1e-61be4add4115\backup\DATA202209130300.zip” file. > Invalid FTP response (A).
9/13/2022 1:23 PM Trying again…
9/13/2022 1:23 PM Destination error: Cannot send command to the server because the response for previous one was not received.
9/13/2022 1:23 PM Trying again…
9/13/2022 1:23 PM Destination error: Cannot send command to the server because the response for previous one was not received.
9/13/2022 1:23 PM Trying again…
9/13/2022 1:23 PM Destination error: Cannot send command to the server because the response for previous one was not received.
9/13/2022 1:23 PM Trying again…
9/13/2022 1:23 PM Destination error: Failed to upload “D:\Backups\SQLBackupAndFTP\SBF\281c292e-89ab-4a0a-9c1e-61be4add4115\backup\DATA202209130300.zip” file to “backups” folder. > Cannot send command to the server because the response for previous one was not received.
9/13/2022 1:23 PM Disconnecting from “FTP” destination “ftp”.

Hello Iouri_Iouchkov,

For the correct work with FTP, we use Rebex libraries. Could you please try to install the following test Rebex client Dropbox - RebexFtpClient.zip - Simplify your life and check if you are able to connect and download a file to your FTP via RebexFtpClien?

Note, the error message you get says that there is no way to send a command to your FTP Server, because the previous command did not receive a response. Could you please contact your FTP Server administrator to check the issue, since the issue doesn’t relate to SQLBackupAndFTP and cannot be resolved from our side.

If you have any other questions, please let us know.

Thank you and sorry for the inconvenience.