Cards stopped validating due to an internal error
Twitter Cards have been working fine since first implemented but have now stopped Validating.
E.G. The above URL was posted and generated a card here:
A repeat test posting of this URL still produced a card due to caching.
However, as soon as I validated the URL using https://cards-dev.twitter.com/validator the cache was cleared and it now fails.
The error coming back is blockedByRobotsImageUrl Which is rubbish, no change had been made, I have even explicitly added Twitterbot/1.0 to the robots.txt
None of our pages are generating cards now.
Has there been some other change with card validation or is there a bug with the bot?
A typical error returned by the validator: