I'm also running into db error #1064 similar to:
https://forum.osticket.com/d/93544-resolved-db-error-1064
https://forum.osticket.com/d/93620-resolved-db-error-1064-part-2/3

How to fix? Is the problem due to creating custom queue? I created then deleted custom queue but problem persists.

DB Error #1064
[SELECT COUNT(DISTINCT CASE WHEN THEN A1.ticket_id END) AS q17, COUNT(DISTINCT CASE WHEN A1.team_id = 0 AND A1.staff_id = 0 THEN A1.ticket_id END) AS q20, COUNT(DISTINCT CASE WHEN THEN A1.ticket_id END) AS q22, COUNT(DISTINCT CASE WHEN THEN A1.ticket_id END) AS q23, COUNT(DISTINCT CASE WHEN THEN A1.ticket_id END) AS q24, COUNT(DISTINCT CASE WHEN A2.state = 'open' THEN A1.ticket_id END) AS q1, COUNT(DISTINCT CASE WHEN A2.state = 'open' AND A2.state = 'open' AND A1.isanswered = '0' THEN A1.ticket_id END) AS q2, COUNT(DISTINCT CASE WHEN (A1.team_id IN (2) OR A1.staff_id IN (1)) AND A2.state = 'open' AND (A1.team_id IN (2) OR A1.staff_id IN (1)) AND A2.state = 'open' AND A1.staff_id IN (1) THEN A1.ticket_id END) AS q6, COUNT(DISTINCT CASE WHEN A2.state = 'closed' AND A2.state = 'closed' AND A1.closed BETWEEN '2019-03-24 01:00:00' AND '2019-03-25 00:59:59' THEN A1.ticket_id END) AS q9, COUNT(DISTINCT CASE WHEN A2.state = 'open' AND A2.state = 'open' AND A1.isanswered = '1' THEN A1.ticket_id END) AS q3, COUNT(DISTINCT CASE WHEN (A1.team_id IN (2) OR A1.staff_id IN (1)) AND A2.state = 'open' AND (A1.team_id IN (2) OR A1.staff_id IN (1)) AND A2.state = 'open' AND NOT A1.staff_id IN (1) THEN A1.ticket_id END) AS q7, COUNT(DISTINCT CASE WHEN A2.state = 'closed' AND A2.state = 'closed' AND A1.closed BETWEEN '2019-03-23 01:00:00' AND '2019-03-24 00:59:59' THEN A1.ticket_id END) AS q10, COUNT(DISTINCT CASE WHEN A2.state = 'open' AND A2.state = 'open' AND A1.isoverdue = '1' THEN A1.ticket_id END) AS q4, COUNT(DISTINCT CASE WHEN (A1.team_id IN (2) OR A1.staff_id IN (1)) AND A2.state = 'open' THEN A1.ticket_id END) AS q5, COUNT(DISTINCT CASE WHEN A2.state = 'closed' AND A2.state = 'closed' AND A1.closed BETWEEN '2019-03-18 01:00:00' AND '2019-03-25 00:59:59' THEN A1.ticket_id END) AS q11, COUNT(DISTINCT CASE WHEN A2.state = 'closed' THEN A1.ticket_id END) AS q8, COUNT(DISTINCT CASE WHEN A2.state = 'closed' AND A2.state = 'closed' AND A1.closed BETWEEN '2019-03-01 01:00:00' AND '2019-04-01 00:59:59' THEN A1.ticket_id END) AS q12, COUNT(DISTINCT CASE WHEN A2.state = 'closed' AND A2.state = 'closed' AND A1.closed BETWEEN '2019-01-01 01:00:00' AND '2019-04-01 00:59:59' THEN A1.ticket_id END) AS q13, COUNT(DISTINCT CASE WHEN A2.state = 'closed' AND A2.state = 'closed' AND A1.closed BETWEEN '2019-01-01 01:00:00' AND '2020-01-01 00:59:59' THEN A1.ticket_id END) AS q14 FROM ost_ticket A1 JOIN ost_ticket_status A2 ON (A1.status_id = A2.id) LEFT JOIN ost_thread A3 ON (A3.object_type = 'T' AND A1.ticket_id = A3.object_id) LEFT JOIN ost_thread_referral A4 ON (A3.id = A4.thread_id) LEFT JOIN ost_staff A5 ON (A4.object_type = 'S' AND A4.object_id = A5.staff_id) LEFT JOIN ost_team A6 ON (A4.object_type = 'E' AND A4.object_id = A6.team_id) LEFT JOIN ost_department A7 ON (A4.object_type = 'D' AND A4.object_id = A7.id) WHERE (A2.state = 'open' AND (A1.staff_id = 1 OR A5.staff_id = 1 OR A1.team_id IN (2) OR A6.team_id IN (2))) OR A1.dept_id IN (1, 3) OR A7.id IN (1, 3)] You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'THEN A1.ticket_id END) AS q17, COUNT(DISTINCT CASE WHEN A1.team_id = 0 AND' at line 1