Troubleshooting High Memory Usage on Client Service Lists
After applying the 8.3.0 update, you may see high memory usage or a partially-loaded page on the client services page (Client Area and Admin Area). You may also see an entry that resembles this example in the PHP Error Log:
PHP Fatal error: Allowed memory size of 134217728 bytes exhausted (tried to allocate 20480 bytes) in /path/to/whmcs/vendor/illuminate/database/Connection.php on line 336
This is caused by the presence of more than one service with the same Domain value.
Apply the 8.3.1 Maintenance Release via the Utilities > Update WHMCS page.
A hotfix has been created for 8.3.0 only to correct this behaviour: