BUG #15021: Postgres crashes unexpectedly

The following bug has been logged on the website:

Bug reference:      15021
Logged by:          Wallace Baggaley
Email address:      wally.baggaley@gmail.com
PostgreSQL version: 9.6.5
Operating system:   Debian GNU Linux 8 container on CentOS 7.2.1511
Description:

Postgres crashes unexpectedly and indicates that it received a signal to end
based on the following logs. But checking user history and journald show
nothing has terminated the application. Is it possible the log "LOG:
received smart shutdown request" could be caused by something other than a
signal. What signals could be associated with this log or is this possibly
related to a crash?

Thanks!
Wally

        January 19th 2018, 11:26:14.710 LOG:  autovacuum launcher started
    January 19th 2018, 11:26:14.706    LOG:  database system is ready to accept
connections
    January 19th 2018, 11:26:14.704    LOG:  MultiXact member wraparound
protections are now enabled
    January 19th 2018, 11:26:14.690    LOG:  invalid record length at 0/88D9C00:
wanted 24, got 0
    January 19th 2018, 11:26:14.690    LOG:  redo is not required
    January 19th 2018, 11:26:14.689    LOG:  database system was not properly shut
down; automatic recovery in progress
    January 19th 2018, 11:26:14.677    LOG:  database system was interrupted; last
known up at 2018-01-19 19:26:04 UTC
    January 19th 2018, 11:26:04.710    LOG:  autovacuum launcher started
    January 19th 2018, 11:26:04.709    LOG:  database system is ready to accept
connections
    January 19th 2018, 11:26:04.707    LOG:  MultiXact member wraparound
protections are now enabled
    January 19th 2018, 11:26:04.698    LOG:  redo done at 0/88D9B68
    January 19th 2018, 11:26:04.698    LOG:  last completed transaction was at log
time 2018-01-19 18:33:58.443636+00
    January 19th 2018, 11:26:04.698    LOG:  invalid record length at 0/88D9B90:
wanted 24, got 0
    January 19th 2018, 11:26:04.694    LOG:  redo starts at 0/88D2B70
    January 19th 2018, 11:26:04.692    LOG:  database system was not properly shut
down; automatic recovery in progress
    January 19th 2018, 11:26:04.678    LOG:  database system was interrupted; last
known up at 2018-01-19 16:41:01 UTC
    January 19th 2018, 10:34:07.436    DETAIL:  Key ("code")=(ABC123) already
exists.
    January 19th 2018, 10:34:07.436    STATEMENT:  insert into "TableName"
("code","subcode")  values ($1,$2)
    January 19th 2018, 10:34:07.436    ERROR:  duplicate key value violates unique
constraint "INDEX_NAME"
    January 19th 2018, 10:34:03.807    STATEMENT:  insert into "TableName"
("code","subcode")  values ($1,$2)
    January 19th 2018, 10:34:03.806    DETAIL:  Key ("code")=(ABC123) already
exists.
    January 19th 2018, 10:34:03.806    ERROR:  duplicate key value violates unique
constraint "INDEX_NAME"
    January 19th 2018, 10:33:58.533    LOG:  autovacuum launcher shutting down
    January 19th 2018, 10:33:58.526    LOG:  received smart shutdown request
    January 19th 2018, 10:33:58.452    DETAIL:  Key ("code")=(ABC123) already
exists.
    January 19th 2018, 10:33:58.452    STATEMENT:  insert into "TableName"
("code","subcode")  values ($1,$2)
    January 19th 2018, 10:33:58.451    ERROR:  duplicate key value violates unique
constraint "INDEX_NAME"