If you try to add a second contact form per page using the TinyMCE button, you can't, you can only edit the 1st form.

If you manually add a new form using the shortcodes, the 2nd one will not appear in the published post if it is different from the first form. If you duplicate the 1st form in the same post, it WILL appear twice, but with the same ID for the form div.

It could be useful to allow more than 1 form per page/post.

Ported from https://plugins.trac.wordpress.org/ticket/1779