Rt4-fcgi crashing frequently

I’m using request tracker 4.4.1 on debian stretch.
As database backend I use postgresql 9.6.15
perl is version 5.24.1
nginx is running as webserver (1.10.3)
I installed request tracker via apt (incl. rt4-fcgi package).

Request tracker is working as expected, but then suddenly, the rt4-fcgi process crashes.
I set up monit (https://mmonit.com/monit/) which checks if the process is runnnig ,otherwise it will try to start it again.
Which means, after the crash I have like a 5 minute downtime.
In the monitoring system I see everytime the RAM usage drops down from rt4 (which is obvious) and postgres.
This happens several times a day (~5-10 times)

The log from rt4-fcgi:

Aug 22 03:45:06 support RT[17747]: [17747] Attempting to use external auth service: ungleich_ldap (/usr/share/request-tracker4/lib/RT/Authen/ExternalAuth.pm:288)
Aug 22 03:45:06 support RT[17747]: [17747] SSO Failed and no user to test with. Nexting (/usr/share/request-tracker4/lib/RT/Authen/ExternalAuth.pm:316)
Aug 22 03:45:06 support RT[17747]: [17747] Autohandler called ExternalAuth. Response: (0, No User) (/usr/share/request-tracker4/html/Elements/DoAuth:58)
Aug 22 03:45:06 support RT[17747]: [17747] Attempting to use external auth service: ungleich_ldap (/usr/share/request-tracker4/lib/RT/Authen/ExternalAuth.pm:288)
Aug 22 03:45:06 support RT[17747]: [17747] SSO Failed and no user to test with. Nexting (/usr/share/request-tracker4/lib/RT/Authen/ExternalAuth.pm:316)
Aug 22 03:45:06 support RT[17747]: [17747] Autohandler called ExternalAuth. Response: (0, No User) (/usr/share/request-tracker4/html/Elements/DoAuth:58)
Aug 22 03:45:07 support RT[17744]: [17744] About to prepare scrips for transaction #29916 (/usr/share/request-tracker4/lib/RT/Transaction.pm:189)
Aug 22 03:45:07 support RT[17744]: [17744] Found 5 scrips for TransactionCreate stage with applicable type(s) Status for txn #29916 on ticket #2480 (/usr/share/request-tracker4/lib/RT/Scrips.pm:482)
Aug 22 03:45:07 support RT[17744]: [17744] Skipping Scrip #11 because it isn't applicable (/usr/share/request-tracker4/lib/RT/Scrips.pm:337)
Aug 22 03:45:07 support RT[17744]: [17744] Skipping Scrip #17 because it isn't applicable (/usr/share/request-tracker4/lib/RT/Scrips.pm:337)
Aug 22 03:45:07 support RT[17744]: [17744] Skipping Scrip #18 because it isn't applicable (/usr/share/request-tracker4/lib/RT/Scrips.pm:337)
Aug 22 03:45:07 support RT[17744]: [17744] Skipping Scrip #19 because it isn't applicable (/usr/share/request-tracker4/lib/RT/Scrips.pm:337)
Aug 22 03:45:07 support RT[17744]: [17744] About to commit scrips for transaction #29916 (/usr/share/request-tracker4/lib/RT/Transaction.pm:212)
Aug 22 03:45:07 support RT[17744]: [17744] Committing scrip #13 on txn #29916 of ticket #2480 (/usr/share/request-tracker4/lib/RT/Scrips.pm:293)
Aug 22 03:45:07 support RT[17744]: [17744] Found 0 scrips for TransactionBatch stage with applicable type(s) Status for txn #29916 on ticket #2480 (/usr/share/request-tracker4/lib/RT/Scrips.pm:482)
Aug 22 03:45:09 support RT[17742]: [17742] Rendering attachment #27056 of 'text/plain' type (/usr/share/request-tracker4/html/Elements/ShowTransactionAttachments:191)
Aug 22 03:45:14 support RT[17744]: [17744] Attempting to use external auth service: ungleich_ldap (/usr/share/request-tracker4/lib/RT/Authen/ExternalAuth.pm:288)
Aug 22 03:45:14 support RT[17744]: [17744] SSO Failed and no user to test with. Nexting (/usr/share/request-tracker4/lib/RT/Authen/ExternalAuth.pm:316)
Aug 22 03:45:14 support RT[17744]: [17744] Autohandler called ExternalAuth. Response: (0, No User) (/usr/share/request-tracker4/html/Elements/DoAuth:58)
Aug 22 03:45:14 support RT[17744]: [17744] Attempting to use external auth service: ungleich_ldap (/usr/share/request-tracker4/lib/RT/Authen/ExternalAuth.pm:288)
Aug 22 03:45:14 support RT[17744]: [17744] SSO Failed and no user to test with. Nexting (/usr/share/request-tracker4/lib/RT/Authen/ExternalAuth.pm:316)
Aug 22 03:45:14 support RT[17744]: [17744] Autohandler called ExternalAuth. Response: (0, No User) (/usr/share/request-tracker4/html/Elements/DoAuth:58)
Aug 22 03:46:47 support systemd[1]: Starting request-tracker4 FastCGI daemon...
Aug 22 03:46:47 support rt4-fcgi[25721]: spawn-fcgi: child spawned successfully: PID: 25725
Aug 22 03:46:47 support rt4-fcgi[25721]: spawn-fcgi: child spawned successfully: PID: 25727
Aug 22 03:46:47 support rt4-fcgi[25721]: spawn-fcgi: child spawned successfully: PID: 25728
Aug 22 03:46:47 support rt4-fcgi[25721]: spawn-fcgi: child spawned successfully: PID: 25729
Aug 22 03:46:47 support rt4-fcgi[25721]: spawn-fcgi: child spawned successfully: PID: 25730
Aug 22 03:46:47 support rt4-fcgi[25721]: spawn-fcgi: child spawned successfully: PID: 25731
Aug 22 03:46:47 support systemd[1]: Started request-tracker4 FastCGI daemon.
Aug 22 03:46:50 support RT[25730]: [25730] Using w3m for HTML -> text conversion (/usr/share/request-tracker4/lib/RT/Interface/Email.pm:1491)
Aug 22 03:46:50 support RT[25730]: [25730] The RTAddressRegexp option is not set in the config. Not setting this option results in additional SQL queries to check whether each address belongs to RT or not. It is especially importa
Aug 22 03:46:50 support RT[25729]: [25729] Using w3m for HTML -> text conversion (/usr/share/request-tracker4/lib/RT/Interface/Email.pm:1491)
Aug 22 03:46:50 support RT[25729]: [25729] The RTAddressRegexp option is not set in the config. Not setting this option results in additional SQL queries to check whether each address belongs to RT or not. It is especially importa
Aug 22 03:46:50 support RT[25731]: [25731] Using w3m for HTML -> text conversion (/usr/share/request-tracker4/lib/RT/Interface/Email.pm:1491)
Aug 22 03:46:50 support RT[25731]: [25731] The RTAddressRegexp option is not set in the config. Not setting this option results in additional SQL queries to check whether each address belongs to RT or not. It is especially importa
Aug 22 03:46:50 support RT[25728]: [25728] Using w3m for HTML -> text conversion (/usr/share/request-tracker4/lib/RT/Interface/Email.pm:1491)
Aug 22 03:46:50 support RT[25728]: [25728] The RTAddressRegexp option is not set in the config. Not setting this option results in additional SQL queries to check whether each address belongs to RT or not. It is especially importa
Aug 22 03:46:50 support RT[25725]: [25725] Using w3m for HTML -> text conversion (/usr/share/request-tracker4/lib/RT/Interface/Email.pm:1491)
Aug 22 03:46:50 support RT[25725]: [25725] The RTAddressRegexp option is not set in the config. Not setting this option results in additional SQL queries to check whether each address belongs to RT or not. It is especially importa
Aug 22 03:46:50 support RT[25727]: [25727] Using w3m for HTML -> text conversion (/usr/share/request-tracker4/lib/RT/Interface/Email.pm:1491)
Aug 22 03:46:50 support RT[25727]: [25727] The RTAddressRegexp option is not set in the config. Not setting this option results in additional SQL queries to check whether each address belongs to RT or not. It is especially importa
Aug 22 03:46:54 support RT[25730]: [25730] Attempting to use external auth service: ungleich_ldap (/usr/share/request-tracker4/lib/RT/Authen/ExternalAuth.pm:288)
Aug 22 03:46:54 support RT[25730]: [25730] SSO Failed and no user to test with. Nexting (/usr/share/request-tracker4/lib/RT/Authen/ExternalAuth.pm:316)
Aug 22 03:46:54 support RT[25730]: [25730] Autohandler called ExternalAuth. Response: (0, No User) (/usr/share/request-tracker4/html/Elements/DoAuth:58)

log from postgresql:

2019-08-22 01:44:12.959 UTC [9198] DEBUG:  performing replication slot checkpoint
2019-08-22 01:44:37.644 UTC [25702] DEBUG:  autovacuum: processing database "postgres"
2019-08-22 01:45:07.824 UTC [25714] DEBUG:  autovacuum: processing database "rtdb"
2019-08-22 01:45:08.613 UTC [17791] request@rtdb LOG:  could not receive data from client: Connection reset by peer
2019-08-22 01:45:08.613 UTC [17791] request@rtdb DEBUG:  unexpected EOF on client connection
2019-08-22 01:45:15.498 UTC [17792] request@rtdb LOG:  could not receive data from client: Connection reset by peer
2019-08-22 01:45:15.498 UTC [17792] request@rtdb DEBUG:  unexpected EOF on client connection
2019-08-22 01:45:15.533 UTC [17807] request@rtdb LOG:  could not receive data from client: Connection reset by peer
2019-08-22 01:45:15.533 UTC [17807] request@rtdb DEBUG:  unexpected EOF on client connection
2019-08-22 01:45:15.534 UTC [17806] request@rtdb LOG:  could not receive data from client: Connection reset by peer
2019-08-22 01:45:15.534 UTC [17806] request@rtdb DEBUG:  unexpected EOF on client connection
2019-08-22 01:45:15.543 UTC [17779] request@rtdb LOG:  could not receive data from client: Connection reset by peer
2019-08-22 01:45:15.543 UTC [17779] request@rtdb DEBUG:  unexpected EOF on client connection

I hope you could help me with this issue.

Cheers