Images inserted in text fields disappear randomly but reappear on cache flush

Intermittently, the images I've inserted into the body of the pages on my website disappear, but reappear after I flush the caches.

It seems clear where the problem is coming from, as the URLs in the HTML to the images are different before and after flush:

Before:

<img width="480" height="178" src="/sites/all/modules/civicrm/bin/sites/default/files/styles/large/public/Picture%20Frame%202_0.jpg" typeof="foaf:Image" class="media-image" alt="">

After:

<img width="480" height="178" src="/sites/default/files/styles/large/public/Picture%20Frame%202_0.jpg" typeof="foaf:Image" class="media-image" alt="">

I've double-checked the filters on my text formats, but nothing stands out as likely to be causing this sort of problem. The order of filters is as follows:

1. Convert URLs into links
2. Convert Media tags to markup
3. Correct faulty and chopped off HTML
4. Correct URLs with Pathologic

What seems particularly odd is that it's intermittent, and (temporarily) fixed by a cache flush.

Perhaps the problem resides somewhere other than in the Media module, but maybe someone has had/solved this problem already? (Couldn't find anything in this issue queue or in CiviCRMs...)