BUG #15021: Postgres crashes unexpectedly

The following bug has been logged on the website:

Bug reference: 15021
Logged by: Wallace Baggaley
Email address: wally(dot)baggaley(at)gmail(dot)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"