Draft Posts Throw 404 on Preview when Supporting post_format

[marklavin]

A client is reporting that they're not able to preview drafts of some of the custom post types we have running on their site. The issue is not occurring for all post types on their site. I believe I've traced the issue to the fact that the errant post types support "post_format."

The preview URL that gets generated when I preview the "ask-the-expert" post is:

​https://www.sitename.com/?post_type=ask-the-expert&p=4063&preview_id=4063&preview_nonce=ebffa07dd9&post_format=standard&_thumbnail_id=-1

That above URL throws a 404 page.

When I pull out the 'post_format=standard' part of the query, so that the URL looks like:

​https://www.sitename.com/?post_type=ask-the-expert&p=4063&preview_id=4063&preview_nonce=ebffa07dd9&_thumbnail_id=-1

then the preview loads correctly.

Interestingly, just for giggles I also tried:

​https://www.sitename.com/?post_type=ask-the-expert&p=4063&preview_id=4063&preview_nonce=ebffa07dd9&_post_format=standard&_thumbnail_id=-1

and that also worked as it should. (notice the added underscore before 'post_format.'

For now I think I'm just going to disable post formats for the offending post types, but methinks I found a bug.