Mistake 1: Two 'Accountables' on the same row. RACI's whole premise is that exactly one person is Accountable per activity. Two accountables means neither is — and the moment something breaks, the finger-pointing tax alone costs weeks.
Mistake 2: Confusing 'Responsible' with 'Consulted'. Legal or Finance often gets tagged R on activities they in fact only review. Result: they end up doing work they shouldn't own, and the true Responsible party quietly slips out of the loop.
Mistake 3: No 'Informed'. Teams downstream get blindsided by decisions taken upstream. A one-line 'Informed' commitment (Slack channel, weekly digest) prevents most of this — but it has to be codified, not implied.
Publish the RACI in the SOP. Reference the SOP in performance reviews. The document only works when it's referenced in consequences.