In drupal.contribution_tracking I noticed a much higher number of visits to the Amazon form coming from our mobile banners than expected, with few leading to a completed donation. Strangely the same wasn't happening on iPad or desktop targeted banners.
Digging in, I found that most had the referrer googleweblight.com/. This appears to be a conversion service Google provide for slow connections (documentation). Visiting https://googleweblight.com/?lite_url=https://en.wikipedia.org does in fact bring up a broken banner, and clicking anywhere on it takes me to the Amazon form.
Without knowing anything about how Google is munging the code to break it so badly, I think the best option is to just hide banners viewed through this site for now. I can do this using CSS, but thought tech might want to investigate a better solution.
(erring on the side of caution by making this private, feel free to open it up if you think that's okay)