Attribution decays through people, not technology: a new campaign built without UTMs, a lead list uploaded with a blank source, a rep overwriting a picklist, a new landing page that skips the tracking code. The model is fine; the human process around it leaks.
Every manual entry point needs a written process, and every programmatic one needs a test. Audit on a clock, not on suspicion — a quarterly review that checks for blank sources, off-taxonomy values and untagged campaigns will catch drift before a board deck does.
Every claim above comes from work LeanScale published. These are the sources.