I have an issue with pages not being returned by search in a public-facing publishing site collection on a production SP2013 (on-prem) farm. The site collection uses managed metadata navigation, and the problem appears to affect all pages that have a friendly URL assigned to them. Because the majority of pages in the site collection have the 'Hide physical URLs from search' page property ticked this results in the pages not being returned in searched results at all.
When I check the crawl logs the pages' structural URLs are being crawled, but not the friendly URLs. I'm not seeing a lot of errors in the crawl logs, and the only search errors I can find in the ULS logs are SSL warnings.
The issue is only occurring in the production farm. In the staging farm, both the structural and friendly URLs are crawled, and friendly URLs are returned in search results.