Yes, this is probably the reason for why your data doesn't get sent to DoubleClick.
This happens when you try to use a 3rd party Sequential HTML javascript item in an event-based rule after the DOM has loaded.
I believe there is a restriction for doing this inside of DTM so that you don't use document.write('<script>//third party script here</script>') after the page has loaded and accidentally replace all of your html. :) But I do know that you can't use Sequential HTML in an event-based rule after the DOM has loaded.
A solution is to use Non-Sequential javascript or Sequential javascript. This solution doesn't use document.write. So, I would suggest copying the javascript and putting it in a javascript rule (not HTML).