Images missing from summary cards


A few days ago we implemented Twitter Cards on our website and got them approved.
Summary: Images with either width or height below 120 pixels won’t show up on summary cards. However, they do appear in search results.

Our main account @heiseonline however won’t show a single image. We’re using the “og:image” fallback. The validator takes a few tries until it finally loads our URLs, but when it does, the page is valid and the image does show up, cropped/resized to a square format.

All our source images used for @heiseonline are max. 100x100, falling well into the given 60x60 and 120x120 dimensions.

However, when I search for one of our tweets, the summary card does show the image:

A different account @heiseautos does show images on the summary cards. The only significant difference seems to be the size of these source images, they’re all larger than 120x120.

There I’ve found only one tweet with a missing summary card image, and it turns out its source image is only 114 pixels high.

Could you please look into this issue?