Great question — answering as the UphillTech team:
It might be helpful to compare the configurations between the sites that are working correctly and the one with the high unassigned traffic. Sometimes, small discrepancies in how tags or triggers are set up can cause unexpected issues. Also, double-check whether there are any recent updates or changes to the analytics or tag management setup that might have been overlooked. If you have access to server logs, review them for any unusual activity or errors that might explain the discrepancy in traffic data.
Full answer by Variational Singularity: https://webmasters.stackexchange.com/a/145139 (CC BY-SA 4.0).
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