We noticed this about two weeks ago - the images on our photo and gallery cards are sometimes right and sometimes wrong. You can look at a card, it will display correctly, refresh the page and then the card shows the wrong image. Usually its one from a previous post. The gallery cards are even more bizarre in that when they display wrong, sometimes one image is correct and then the other three are wrong. Here’s the weird part though - sometimes, if you refresh the page, they will either display the correct image(s) or a completely different set of wrong images. We are flummoxed but it feels like a cache or content-distribution thing. We have checked and re-checked our meta-data. We cannot find a problem and the twitter card validator shows everything is correct on our end as well for every url we have checked (dozens)
Very frustrating. We love the cards , but the current situation is making us look pretty bad.