I’ve had a similar problem since the update, and have located an error, the plugin seems to be requesting an image from the domain server which does not exist. This took my Vps cpus out with 20 sites all using WPO plugin, each requesting the same wpo logo image file which is not on my server. But the request’s overwhelmed the server.
/wp-content/uploads/wpo/images/wpo_logo_small.png
currently all domains have the plugin deactivated
regards Nigel Bedingfield