Apache log contains lots of errors too ->
[Tue Oct 16 20:50:49.322341 2018] [:error] [pid 8163] [client ....:36748] PHP Fatal error: Uncaught exception 'InvalidArgumentException' with message 'List indices should be integers' in /home/XYZ/web/include/class.util.php:149\nStack trace:\n#0 /home/XYZ/web/include/class.forms.php(81): ListObject->offsetExists('message')\n#1 /home/XYZ/web/include/class.ticket.php(3564): Form->getField('message')\n#2 /home/XYZ/web/scp/tickets.php(329): Ticket::open(Array, Array)\n#3 {main}\n thrown in /home/XYZ/web/include/class.util.php on line 149, referer: http://XYZ.net/scp/tickets.php?a=open
[Tue Oct 16 21:01:32.985850 2018] [:error] [pid 9632] [client ....5356] PHP Fatal error: Uncaught exception 'InvalidArgumentException' with message 'List indices should be integers' in /home/XYZ/web/include/class.util.php:149\nStack trace:\n#0 /home/XYZ/web/include/class.forms.php(81): ListObject->offsetExists('email')\n#1 /home/XYZ/web/account.php(72): Form->getField('email')\n#2 {main}\n thrown in /home/XYZ/web/include/class.util.php on line 149, referer: http://XYZ.net/account.php?do=create
[Tue Oct 16 21:02:02.949059 2018] [:error] [pid 9631] [client ...:5490] PHP Fatal error: Uncaught exception 'InconsistentModelException' with message 'Unable to prepare query: SELECT A4.staff_id
AS lock__staff_id
, A1.staff_id
AS staff_id
, A1.isoverdue
AS isoverdue
, A1.team_id
AS team_id
, A1.ticket_id
AS ticket_id
, A1.number
AS number
, A2.subject
AS cdata__subject
, A6.address
AS user__default_email__address
, A1.source
AS source
, A3.priority_color
AS cdata__:priority__priority_color
, A3.priority_desc
AS cdata__:priority__priority_desc
, A1.status_id
AS status_id
, A7.name
AS status__name
, A7.state
AS status__state
, A1.dept_id
AS dept_id
, A8.name
AS dept__name
, A5.name
AS user__name
, A1.lastupdate
AS lastupdate
, A1.isanswered
AS isanswered
, B0.firstname
AS staff__firstname
, B0.lastname
AS staff__lastname
, B1.name
AS team__name
, (SELECT COUNT(R0.id
) AS count
FROM ost_thread
Q7 JOIN ost_ticket
Q8 ON (Q7.object_type
= 'T' AND Q7.object_id
= Q8.ticket_id
) LEFT JOIN ost_thread_collaborator
R0 ON (Q7.`id in /home/XYZ/web/include/class.orm.php on line 3137, referer: http://XYZ.net/scp/login.php