we are stumped fixing this problem. It eventually just fixed itself.
We installed SSL, changed
settings -> general URL to point to https version of the site. All assets seem to load just fine. However, we noticed today that one specific page has the mixed content warning and didn't load assets. All other pages were fine. Then, 10 or so minutes later, this page resolved itself and it loaded via https. All was fine! We didn't change a single thing.
What could cause an occasional "outage" of loading content over ssl?
We are using total cache plugin, but are not using a cdn. I did not try turning off or clearing cache.
We have not edited wp_config.php to force ssl or anything...may try that next.
We cannot find any hardcoded http links in the codebase. The theme seems to have set all asset loads and we aren't including any customs ones (not that I can find).
Still digging on this but if anyone out there has any insight it would be greatly appreciated!!
post_content? W3TC would definitely contribute to this as I've seen this before on one of our sites. I would recommend you do a complete purge of object, and page caches.