Debug a jQuery Lightbox Plugin

I have written a jQuery plugin that is essentially a lightbox which can display images, media and HTML content. Part of the plugin resizes the image + caption to make sure it is visible on the page and not cropped or stretched. It is working fine across all browsers and devices apart from a very particular scenario – square images on Safari iOS. I am not an expert in writing jQuery plugins, so don't expect it to be well structured. I will communicate closely with the developer to clarify things about how the plugin works. If I am happy with how things go, I will engage the developer for another job to improve the structure of the plugin.