My Adsense ads are intermittently not appearing.

I have tried different browsers, cleared caches, used the default theme and still the Adsense ads sometimes do not appear. It seems particularly reproducible in a post vs. the board index.

Examining the source in the browser indicates that the Adsense code is being served.

Here's is an example of a page that has the problem. 3 Ads should appear on this page. Top header, After the post, Footer

https://www.ibspatient.org/community/topic/28208-pubmed-what-impact-do-rome-iv-criteria-have-on-patients-with-ibs-in-china/

I am using vanilla Adsense code in Site Promotion -> Advertisements

Has anybody experienced this behavior before?

Put some text after your adsense code and see if that comes up/gets served. If it does, its not IPS. 

The word "Advertisement" comes up under the box for the ad. It's showing up fine.

I've opened a ticket with Google.

yeah then its probably something with your ad code.

It almost seems like a caching issue as the same ad code works fine on the main board index, but intermittently not on posts or forum indexes.