by Ken Task.
Back to OP's problem ...
There's a couple of things I've discovered on 'large' course backups (large here doesn't necessarily mean many files ... but 'large' processing ... like with Quizzes):
PHP max_input_vars increased from default ... which I think is 1000 to something larger ... 2 or 3 thousand.
And the unloading of Zend php xcode. See anything related to that in php -m at the bottom for Zend extensions. Not really needed to run Moodle and it had some restrictions that affected Moodle.
'spirit of sharing', Ken