We've run into an issue with displaying videos on pages. Our sign-up page asks users to include a vimeo link. This field is displayed on another page and the video does not embed. The process works if we manually edit the URL in the field. The issue is similar to this closed bug: http://nationbuilder.com/embedly_links_not_automatically_embedding_on_nationbuilder_pages Please contact Shen-Shen on your services team for the specific workflow that has allowed your support team to replicate the bug.
Unfortunately, NationBuilder does not unfurl embed.ly links that are inputted through custom fields on a form. I do understand you've created a workflow within the template that takes Vimeo link and wraps them within the <iframe> tag so that it displays in the public profile page. This is definitely an excellent workaround.
Last, to clarify, embed.ly links ought to unfurl on certain user submitted posts, like blog posts and public profiles submissions. I understand there was a misunderstanding about this, but just wanted to clarify. You can simply add the embed.ly eligible link as is, and it will display the video.