I'm trying to debug a problem with WHMCS (domains/hosting billing script, now partially owned by cPanel). Some multiple domain registrations are failing silently, without anything being logged anywhere. It looks like the process simply dies or times out and leaves no trace. There's nothing in the PHP error_log, nor on the application own error logs. What can I enable to troubleshoot this? I would like to have as much error logging as possible. I would also like to increase any parameters that I can increase that could help with performance/avoiding timeouts. Any tips?