I had same problem…update to version 3.1.9 of Restrict Content crashed my site. Thanks to asaynisch for suggesting commenting-out lines 130-131 of restrictcontent.php. This solved the problem immediately and the plugin is now operating normally.
Thanks so much, KZeni for writing this brilliant patch and jagp for your helpful comments. The patch works perfectly with version 4.9.1 of Contact Form 7 and Flamingo version 1.7.