Custom style only working in dynamic mode, not static

I have a custom text box style I’ve setup, but after updating the plugin today, my custom attributes do not work with the static mode. They work fine if I switch to dynamic mode, but I need to run static mode for performance.

You can see an example at http://socalhiker.net/hiking-the-metolius-river-trail/ where the “Trail Details” is a special text box that uses the custom style.

This custom style includes a green caption background and green borders, but when running static mode, these appear to be white.

https://wordpress.org/plugins/wp-special-textboxes/