unknown postgres ssl error "could not accept SSL connection: Success" and timeout

Ubuntu 18.04.6 LTS (GNU/Linux 4.15.0-167-generic x86_64)

OpenSSL 1.1.1 11 Sep 2018

Sometimes i see this in postgres logs

Found some similar threads, but not sure

https://github.com/modoboa/modoboa/issues/1702

https://postgrespro.com/list/thread-id/2585389

How i can to debug this?

2023-02-22 00:43:38.570 MSK [27636] [unknown](at)[unknown] LOG: could
not accept SSL connection: Success
2023-02-22 00:43:38.570 MSK [27631] [unknown](at)[unknown] LOG: could
not accept SSL connection: Success
2023-02-22 00:43:38.570 MSK [27639] [unknown](at)[unknown] LOG: could
not accept SSL connection: Success
2023-02-22 00:43:38.570 MSK [27642] [unknown](at)[unknown] LOG: could
not accept SSL connection: Success
2023-02-22 00:43:38.570 MSK [27643] [unknown](at)[unknown] LOG: could
not accept SSL connection: Success
2023-02-22 00:43:38.570 MSK [27627] [unknown](at)[unknown] LOG: could
not accept SSL connection: Connection reset by peer

CRITICAL
PDOException
SQLSTATE[08006] [7] timeout expired
PDOException
/var/log/web/hub2.log
Feb 21, 2023 @ 23:43:38.001
CRITICAL
PDOException
SQLSTATE[08006] [7] timeout expired
PDOException
/var/log/web/hub2.log
Feb 21, 2023 @ 23:43:38.001
CRITICAL
PDOException
SQLSTATE[08006] [7] timeout expired
PDOException
/var/log/web/hub2.log

here is my postgres config

cat /etc/postgresql/12/main/postgresql.conf

data_directory = '/var/lib/postgresql/12/main'
hba_file = '/etc/postgresql/12/main/pg_hba.conf'
ident_file = '/etc/postgresql/12/main/pg_ident.conf'
external_pid_file = '/var/run/postgresql/12-main.pid'

listen_addresses = '*'
port = 5432
max_connections = 10000
unix_socket_directories = '/var/run/postgresql'
ssl = on
ssl_cert_file = '/etc/ssl/certs/ssl-cert-snakeoil.pem'
ssl_key_file = '/etc/ssl/private/ssl-cert-snakeoil.key'

shared_buffers = 4GB
temp_buffers = 8MB
work_mem = 128MB
maintenance_work_mem = 128MB
dynamic_shared_memory_type = posix

bgwriter_lru_maxpages = 0
effective_io_concurrency = 3

wal_level = hot_standby

checkpoint_completion_target = 0.9

archive_mode = on
archive_command = '/bin/true'
archive_timeout = 300

max_standby_archive_delay = 21600
max_standby_streaming_delay = 21600

I should to update my openssl to see real error? How can i do that if
i use ubuntu 18.04?