Short description of your issue:

For an amp-carousel that is visible on the initial load, an amp-ad in the first slide does not (regularly) trigger. Very occasionally it does load (it is more frequent when dev tools is open) so it seems to be a race condition between amp-ad and amp-carousel. All other slides after the inital load render the ad correctly, and going back to the first slide after moving away will then correctly render the ad.

How do we reproduce the issue?

https://www.forbes.com/test/krogers/ampadinampcarousel.html

Land on the page, there is an amp-ad tag on top of the first slide, but it does not load. Go to the next slide, there is also an ad on top of the next slide and it should load. Go back to the first slide and you can see the first ad load.

Note that sometimes it will load if you have dev tools open, it seems like there is a race condition so the dev tools must slow it down for long enough that the amp-ad can load.

What browsers are affected?

So far I've only tested it in desktop chrome and android chrome (both current) and it is happening in both places.

Which AMP version is affected?

The amp version is Version 1491601970987. I only attempted to try this yesterday after a recommendation from the amp team for this to be the way to implement something akin to a mobile ad that refreshes on slide change (attempting to replicate gallery pages)