Problem with backup

Hello,

I have a problem when I try to create a backup of my server. The backup process stops and in the logs it seems that it restarts every five minutes without generating a tar file.
The logs show the following:

-- SYSTEM --
2021-06-08 14:25:02 admin.conf
2021-06-08 14:25:02 stats.log
2021-06-08 14:25:02 history.log
2021-06-08 14:25:02 pam


-- WEB --
2021-06-08 14:25:02 onyx.crystalweb.xyz
2021-06-08 14:25:02 crystalweb.xyz
2021-06-08 14:25:03 crystalengine.xyz
2021-06-08 14:25:03 whiteblue.xyz
2021-06-08 14:25:04 whiteblue.events
2021-06-08 14:25:08 saylogonow.com
2021-06-08 14:25:08 xristina-dance-academy.gr
2021-06-08 14:25:08 thinslicingdesign.com
2021-06-08 14:25:08 spring-dance-cup.com
2021-06-08 14:25:13 zkpromo.com
2021-06-08 14:25:13 goudeliaballetschool.gr
2021-06-08 14:25:15 ditashipping.com
2021-06-08 14:25:18 proesthetic.gr
2021-06-08 14:25:19 wanderingcynthia.com
2021-06-08 14:25:21 hellenicroots.gr
2021-06-08 14:25:22 cressidajewels.com
2021-06-08 14:25:22 santorini-roadtrips.com
2021-06-08 14:25:24 mykonos.travel
2021-06-08 14:25:24 *** 18 domains ***

-- DNS --
2021-06-08 14:25:24 *** 0 domains ***

-- MAIL --
2021-06-08 14:25:24 *** 0 domains ***

-- DB --
2021-06-08 14:25:24 admin_wbt (mysql)
sh: 0: getcwd() failed: No such file or directory
sh: 0: getcwd() failed: No such file or directory
shell-init: error retrieving current directory: getcwd: cannot access parent directories: No such file or directory
job-working-directory: error retrieving current directory: getcwd: cannot access parent directories: No such file or directory
sh: 0: getcwd() failed: No such file or directory
shell-init: error retrieving current directory: getcwd: cannot access parent directories: No such file or directory
job-working-directory: error retrieving current directory: getcwd: cannot access parent directories: No such file or directory
sh: 0: getcwd() failed: No such file or directory
exim: getting initial cwd failed: No such file or directory
Error: dump admin_wbt failed

Any help will be appreciated. Thank you in advance.

Here is the issue but don’t see anything wrong on my machines

Are you able to add a database?

Yes, I can add and delete databases.
Everything else works flawlessly.

Is there enough disk space available on both servers?

Yes

/dev/ploop35791p1 30G 8.2G 20G 29% /

I guess it is adequate…
A couple of days ago though there was another website around 6GB. There was indeed not enough space but it is now removed.