Whenever you have a featured image selected, and you choose one of the smaller thumbnails to switch to and zoom in on, you are no longer able to switch back to the original featured image with this plugin. It is overtaken by the newer pictures. Only way to see the original featured image again is to refresh the page.
There was a solution posted here but It does not longer work. The line that should be commented is no longer present in the latest woocommerce version.