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this is an underrated issue in ppc tracking.. ga4 often silently reports incorrect data without showing any errors, which leads to fragmented data over time. if utm_medium is incorrect, it can break channel grouping, so paid social and other channels may be shown incorrectly. even with perfect utm setup, ga4 cannot capture all sessions due to adblockers, ios restrictions, and dark social, which can lead to 70-80% data missing. utm audits often reveal multiple variants of the same source, which can lead to long-term budget misallocation..
