This SQL fails for zabbix frontend:

2022-04-20 05:11:35.299 EDT [2232] ERROR:  could not find pathkey item to sort
2022-04-20 05:11:35.299 EDT [2232] STATEMENT:  SELECT DISTINCT COUNT(DISTINCT t.triggerid) AS rowscount,i.hostid FROM triggers t,functions f,items i WHERE i.hostid=62298 AND f.triggerid=t.triggerid AND f.itemid=i.itemid AND t.flags IN (0,4) GROUP BY i.hostid

Release notes for postgresql 13.3 includes a bugfix with the description:

Fix “could not find pathkey item to sort” planner errors in some situations where the sort key involves an aggregate or window function (James Coleman, Tom Lane)
https://www.postgresql.org/docs/13/release-13-3.html

Suggestion is to include this information to know issues in Zabbix documentation - https://www.zabbix.com/documentation/current/en/manual/installation/known_issues