Error 4.3.0 Error: queue file write error. (Postfix + Dovecot + MySQL)?

Question

MySQL

Hi all!
There was a problem, I set up a mail server, the number of mailboxes is 150-200,
At first everything was ok, but recently, I periodically see an error on clients:
Ошибка 4.3.0 Error: queue file write error.
there is space on the disk

Size  Used Avail Use%
1.8T  465G  1.3T  27%

In the syslog

Oct 16 20:30:42 production postfix/cleanup[4049]: warning: mysql:/etc/postfix/sql/valias.cf lookup error for "[email protected]"
Oct 16 20:30:42 production postfix/cleanup[4049]: warning: 8F3EA340511: virtual_alias_maps map lookup problem for [email protected] -- message not accepted, try again later

Dovecot.log

Warning: autocreate plugin is deprecated, use mailbox { auto } setting instead

in mysql

mysql> show variables like "max_connections";
+-----------------+-------+
| Variable_name   | Value |
+-----------------+-------+
| max_connections | 300   |
+-----------------+-------+
1 row in set (0.00 sec)

mysql> show full processlist;
+------+-------------+-----------+-----------+---------+------+----------+-----------------------+
| Id   | User        | Host      | db        | Command | Time | State    | Info                  |
+------+-------------+-----------+-----------+---------+------+----------+-----------------------+
|  544 | root        | localhost | NULL      | Sleep   | 2725 |          | NULL                  |
| 6265 | root        | localhost | NULL      | Sleep   |  705 |          | NULL                  |
| 6776 | postfixuser | localhost | postfix   | Sleep   |   17 |          | NULL                  |
| 8062 | sitesi      | localhost | sitesi-ru | Sleep   |   19 |          | NULL                  |
| 8084 | root        | localhost | NULL      | Query   |    0 | starting | show full processlist |
| 8090 | sitesi      | localhost | sitesi-ru | Sleep   |    0 |          | NULL                  |
| 8091 | sitesi      | localhost | sitesi-ru | Sleep   |    0 |          | NULL                  |
| 8101 | sitesi      | localhost | sitesi-ru | Sleep   |    0 |          | NULL                  |
+------+-------------+-----------+-----------+---------+------+----------+-----------------------+
8 rows in set (0.00 sec)

postfix main.cf

spoiler

myhostname = mail.sitesi.ru
mydomain = sitesi.ru
myorigin = $mydomain

alias_maps = hash:/etc/aliases
alias_database = hash:/etc/aliases
mydestination = $myhostname,localhost.$myhostname,localhost

relayhost =
mynetworks = 127.0.0.0/8
mailbox_command = procmail -a "$EXTENSION"
mailbox_size_limit = 0
recipient_delimiter = +
inet_interfaces = all
inet_protocols = ipv4
message_size_limit = 51200000

virtual_mailbox_domains = mysql:/etc/postfix/sql/vdomains.cf
virtual_mailbox_base = /var/vmail
virtual_mailbox_maps = mysql:/etc/postfix/sql/vmailbox.cf
virtual_alias_maps = mysql:/etc/postfix/sql/valias.cf
virtual_minimum_uid = 1150
virtual_uid_maps = static:1150
virtual_gid_maps = static:8

virtual_transport = dovecot
dovecot_destination_recipient_limit = 1
smtpd_banner = $myhostname ESMTP $mail_name (Debian/GNU)

biff = no
append_dot_mydomain = no
readme_directory = no 

smtpd_sasl_type = dovecot
smtpd_sasl_path = private/auth
smtpd_sasl_auth_enable = yes
broken_sasl_auth_clients = yes
smtpd_sasl_security_options = noanonymous
smtpd_sasl_local_domain =
smtpd_sasl_exceptions_networks = $mynetworks
smtpd_sasl_authenticated_header = yes

# TLS 
smtpd_tls_cert_file=/etc/postfix/certs/cert.pem
smtpd_tls_key_file=/etc/postfix/certs/key.pem
smtpd_use_tls=yes
smtpd_tls_session_cache_database = btree:${data_directory}/smtpd_scache
smtp_tls_session_cache_database = btree:${data_directory}/smtp_scache
smtpd_tls_mandatory_protocols=!SSLv2,!SSLv3
smtp_tls_note_starttls_offer = yes
smtpd_tls_loglevel = 1
smtpd_tls_received_header = yes
smtpd_tls_session_cache_timeout = 3600s
tls_random_source = dev:/dev/urandom
smtpd_tls_security_level = may
smtp_tls_security_level = may

#SMTPD parameters
unknown_local_recipient_reject_code = 450
maximal_queue_lifetime = 7d
minimal_backoff_time = 1000s
maximal_backoff_time = 8000s
smtp_helo_timeout = 60s
smtpd_recipient_limit = 80
smtpd_soft_error_limit = 3
smtpd_hard_error_limit = 12

smtpd_sender_restrictions =     
          permit_sasl_authenticated,
          permit_mynetworks,
          warn_if_reject reject_non_fqdn_sender,
          reject_unknown_sender_domain,
          reject_unauth_pipelining,
          #permit

smtpd_client_restrictions = 
          reject_rbl_client cbl.abuseat.org,
            reject_rbl_client dialups.mail-abuse.org,
            reject_rbl_client bl.spamcop.net,
            reject_rbl_client zen.spamhaus.org,
            reject_rbl_client sbl-xbl.spamhaus.org,
 
smtpd_recipient_restrictions = 
          reject_unauth_pipelining,
          permit_mynetworks,
          permit_sasl_authenticated,
          reject_non_fqdn_recipient,
          reject_unknown_recipient_domain,
          reject_unauth_destination,
          #permit