Featured images randomly(?) fail but some show on reload

The featured images on some of my posts fail to show up on the front page. Sometimes they will all re-appear after a refresh, but refreshing again (or navigating away and back) then some of them will fail again.

Tried deactivating plugins, purging cache, using a cache plugin, re-uploading the images, using tiny images, etc. Problem occurs on all browsers and devices, but not with the first two posts I created and I can’t find anything different between the first ones and later posts.

http://www.mattsfavoritethings.com
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