Advertisements intermittently not loading

Initial request from Jen: I'm noticing today that we are periodically not seeing ad units load on Sahara Reporters - this seems to be happening about half of the time. From what I can see, the ad code isn't firing at all, so requests aren't making it to the ad server:

The ad code still exists in the page source code. There were JavaScript errors in the console, but fixing the JavaScript errors did not fix the initial reported issue of ads not showing.