Db_Exception

I migrated my webissues instance to a new server. When admin users log in there is no issue. When regular users login, however, we see the following:

Unexpected Error

An unexpected error occured while processing the request.

The event log is as follows:

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Event Details

Type:Errors

Severity: Error

Date:06/04/2018 09:55

Message:Unhandled System_Db_Exception: in /var/www/html/webissues/system/db/mysqli/engine.inc.php on line 287
Stack trace:
#0 /var/www/html/webissues/system/db/mysqli/engine.inc.php(110): System_Db_Mysqli_Engine->handleError(Object(mysqli))
#1 /var/www/html/webissues/system/db/mysqli/engine.inc.php(90): System_Db_Mysqli_Engine->executeStatement('SELECT COUNT(*)...', Array)
#2 /var/www/html/webissues/system/db/connection.inc.php(256): System_Db_Mysqli_Engine->query('SELECT COUNT(*)...', Array)
#3 /var/www/html/webissues/system/db/connection.inc.php(356): System_Db_Connection->queryArgs('SELECT COUNT(*)...', Array)
#4 /var/www/html/webissues/system/db/connection.inc.php(343): System_Db_Connection->queryScalarArgs('SELECT COUNT(*)...', Array)
#5 /var/www/html/webissues/system/api/projectmanager.inc.php(683): System_Db_Connection->queryScalar('SELECT COUNT(*)...', 7, 2)
#6 /var/www/html/webissues/client/projectstree.inc.php(66): System_Api_ProjectManager->getProjectsCount()
#7 /var/www/html/webissues/system/web/component.inc.php(100): Client_ProjectsTree->execute()
#8 /var/www/html/webissues/system/web/view.inc.php(247): System_Web_Component->run()
#9 /var/www/html/webissues/client/index.html.php(22): System_Web_View->insertComponent('Client_Projects...')
#10 /var/www/html/webissues/system/web/view.inc.php(284): include('/var/www/html/w...')
#11 /var/www/html/webissues/system/web/view.inc.php(217): System_Web_View->executeTemplate()
#12 /var/www/html/webissues/system/web/component.inc.php(102): System_Web_View->render()
#13 /var/www/html/webissues/system/web/application.inc.php(77): System_Web_Component->run()
#14 /var/www/html/webissues/system/core/application.inc.php(210): System_Web_Application->execute()
#15 /var/www/html/webissues/system/bootstrap.inc.php(133): System_Core_Application->run()
#16 /var/www/html/webissues/client/index.php(61): System_Bootstrap::run('Common_Applicat...', 'Client_Index')
#17 {main}

User name: Me

Host name:10.10.255.105

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I have reviewed similar issues reported any my my,.cnf file already includes the following lines:

table_open_cache        = 16384
table_definition_cache  = 16384
tmp_table_size          = 64M
join_buffer_size        = 512M

Any suggestions would be appreciated.

For reference:

Ubuntu 16.04 LTS
Apache 2.4.18
PHP 7.0.30
MySQL 5.5.60

Thanks.