PostgreSQL background process raising errors - postgresql

Question

At about 7:45 this morning, errors started appearing in our customer's PostgreSQL logs. Nobody from my company was working on their system at that time. The error messages have nothing to do with our client's database or the software that we provided. As far as I can tell, the software we provided is operating normally.
Can anyone tell me what might be happening and how to correct it?
This is an ancient PostgreSQL installation: version 8.1 running on Windows Server 2003. We've never updated it because it is still working.
2019-08-08 07:43:23 FATAL: unrecognized configuration parameter "application_name"
2019-08-08 07:43:32 FATAL: unrecognized configuration parameter "application_name"
2019-08-08 07:43:52 FATAL: unrecognized configuration parameter "application_name"
2019-08-08 07:43:52 ERROR: syntax error at or near "has_priviledge" at character 90
2019-08-08 07:43:52 STATEMENT:
SELECT
has_table_privilege(
'pgagent.pga_job', 'INSERT, SELECT, UPDATE'
) has_priviledge
WHERE EXISTS(
SELECT has_schema_privilege('pgagent', 'USAGE')
WHERE EXISTS(
SELECT cl.oid FROM pg_class cl
LEFT JOIN pg_namespace ns ON ns.oid=relnamespace
WHERE relname='pga_job' AND nspname='pgagent'
)
)
2019-08-08 07:43:53 ERROR: column "state" does not exist
2019-08-08 07:43:53 STATEMENT: /*pga4dash*/
SELECT 'session_stats' AS chart_name, row_to_json(t) AS chart_data
FROM (SELECT
(SELECT count(*) FROM pg_stat_activity) AS "Total",
(SELECT count(*) FROM pg_stat_activity WHERE state = 'active') AS "Active",
(SELECT count(*) FROM pg_stat_activity WHERE state = 'idle') AS "Idle"
) t
UNION ALL
SELECT 'tps_stats' AS chart_name, row_to_json(t) AS chart_data
FROM (SELECT
(SELECT sum(xact_commit) + sum(xact_rollback) FROM pg_stat_database) AS "Transactions",
(SELECT sum(xact_commit) FROM pg_stat_database) AS "Commits",
(SELECT sum(xact_rollback) FROM pg_stat_database) AS "Rollbacks"
) t
UNION ALL
SELECT 'ti_stats' AS chart_name, row_to_json(t) AS chart_data
FROM (SELECT
(SELECT sum(tup_inserted) FROM pg_stat_database) AS "Inserts",
(SELECT sum(tup_updated) FROM pg_stat_database) AS "Updates",
(SELECT sum(tup_deleted) FROM pg_stat_database) AS "Deletes"
) t
UNION ALL
SELECT 'to_stats' AS chart_name, row_to_json(t) AS chart_data
FROM (SELECT
(SELECT sum(tup_fetched) FROM pg_stat_database) AS "Fetched",
(SELECT sum(tup_returned) FROM pg_stat_database) AS "Returned"
) t
UNION ALL
SELECT 'bio_stats' AS chart_name, row_to_json(t) AS chart_data
FROM (SELECT
(SELECT sum(blks_read) FROM pg_stat_database) AS "Reads",
(SELECT sum(blks_hit) FROM pg_stat_database) AS "Hits"
) t