Scheduled backup fails

Virtualmin
1

I have created a scheduled backup. It was working fine but now I have a problem while 3 virtual server backups are uploaded via FTP to another server. All another virtual servers backups successfully. There is a problem just with these 3 (they are the biggest ones, each server backup is about 10 Gb).
Here is the backup log:

Backup failed! See the progress output above for the reason why. Total backup time was 9 hours, 58:21 minutes.
Virtual servers that failed :
xxx.xx
yyy.yy
zzz.zz
Sent by Virtualmin at: https://xxxxx.yyy:10000
…
Uploading archive to FTP server xxx.xxx.xxx.xxx…
… upload failed! initial connection failed : ransfer complete

… completed in 2 hours, 13:23 minutes
…

Archive with a backup is created on FTP server (.tar.gz) and I can download and extract files from there, but no other files are created (.tar.gz.dom and .tar.gz.info). A backup log is strange: there is “failed” and “complete” words at the same time and no letter “T” in “Transfer complete” words, just “ransfer complete”.
Is it a bug?

2

I noticed that backup process uploads .tar.gz file 3 times. It transfers 100% and starts upload again with archive file overwriting.

3

Can you ftp to the receiving server? Does it have enough disk space?

4

Yes, there are much space available. The backups are making every day. No problem with space.

5

I have tried to make a backup to another FTP server. All was completed successfully. Problem FTP server runs Proftpd.

6

I configured Proftpd with such params:
“AllowStoreRestart on”
“AllowRetrieveRestart on”
and it doesn’t helped.

Backup file is uploading to 100% and upload starts from the beggining, This repeates 3 times and then error.