Mantra Settings & Zend OPcache

I have a curious little problem. Just upgraded my WP site and running the following versions of software:

WordPress 3.9.2
Mantra 2.3.4

PHP version info:
# php -v
PHP 5.4.31 (cli) (built: Aug 7 2014 08:11:40)
Copyright (c) 1997-2014 The PHP Group
Zend Engine v2.4.0, Copyright (c) 1998-2014 Zend Technologies
with the ionCube PHP Loader v4.6.1, Copyright (c) 2002-2014, by ionCube Ltd., and
with Zend Guard Loader v3.3, Copyright (c) 1998-2013, by Zend Technologies
with Zend OPcache v7.0.3, Copyright (c) 1999-2014, by Zend Technologies

With OPcache enabled I can’t edit the Mantra Settings. This problem occurs with all plugins disabled. I get the jQuery error:
—
Checking jQuery functionality…
If this message remains visible after the page has loaded then there is a problem with your WordPress jQuery library. This can have several causes, including incompatible plugins. The Parabola Settings page cannot function without jQuery.
—
Just the following 4 menu items appear and can’t be expanded:
Layout Settings
Header Settings
Presentation Page
Text Settings

In the Apache global error log I get (with hostname & IP address obscured by me):
[Sat Aug 09 12:08:37 2014] [warn] [client x.x.x.x] (104)Connection reset by peer: mod_fcgid: error reading data from FastCGI server, referer: https://mysite/wp-admin/theme-editor.php
[Sat Aug 09 12:08:37 2014] [warn] [client x.x.x.x] (104)Connection reset by peer: mod_fcgid: ap_pass_brigade failed in handle_request_ipc function, referer: https://mysite/wp-admin/theme-editor.php
[Sat Aug 09 12:08:43 2014] [error] mod_fcgid: process /usr/local/cpanel/cgi-sys/php5(18291) exit(communication error), get unexpected signal 11

There’s no PHP errors logged. I think PHP may be segfaulting (the signal 11).
Now if I disable OPcache the menu settings work!
I tried blacklisting anything in OPcache (e.g even blacklisting ‘*’) – no luck. I’ve tried default OPcache settings. I could switch back to APC but I like OPcache!
Oh, I’m using the FCGI PHP handler. I get different results (but still broken) when using DSO.