"Unspecified" in breakdown of Marketing Channels by Tracking Code
Hello!
I have a specific set of Marketing Channels that depend on the tracking code to categorize traffic. I can see traffic on all of these channels. However, if I do a breakdown by Tracking Code, I get a large chunk of all metrics attributed to "Unspecified".
Below is a screenshot of this ocurring with Paid Search:

What could be causing this? I ran Omnibug and sent tagged traffic to my site. I can see that, on the first visited page, the xdm.marketing.trackingCode is filled with the correct CID, but on subsequent page views the field comes up empty. Is this the intended behaviour?
All your help is much appreciated, this is driving me a little insane. Thank you so much for any guidance you can give me :)!
All the best,
Diego