Have you tried wordpress debug mode or are your server logs specifically erroring on any specific file? I know when I was troubleshooting another plugin it pointed me to at least the file generating the error. Does the error occur in Admin only and does it disable your site completely, just disable the plugin, or does it disable admin but not the none-logged in user and to external users otherwise seems fine?
I was running an older version of PHP and upgraded to 5.6 I believe, 5.3 is EOL as of August and 5.4 is coming EOL in June. The recommended version is 5.5 at a minimum usually right now. That may also be something to try.
https://php.net/supported-versions.php
Christopher