Quote Originally Posted by lat9 View Post
OPC's AJAX handler (which comes into play when the shipping method is changed) loads the current template's version of the various tpl_modules_opc_*.php files.

Are there, perchance, some leftover FEC files that are coming into play?
Not that I'm aware of. I took a download of the FEC module and deleted any matching files that existed on the site.

Can you confirm that it's not expected and/or deliberate behaviour for the class names to be getting stripped of the form fields?