We noticed twitter cards showing up in our feeds today. Awesome.
We’re seeing one occasional issue. In some cases, the thumbnails aren’t being created and result in a broken image placeholder within the tweet.
I’ve been looking for issues in our meta tags, but everything is identical between the image that do and don’t work. I seem to be able to resolve the issue by revisiting the “details” tweet page a few times.
Example url that didn’t work: https://twitter.com/aviewfrommyseat/status/237908922680360961
We had to reload the page a few times for the thumb to get generated properly.
All my images in the twitter:image meta are 800px wide, though the heights vary.
Hope this helps,