Chargebacks -40%. Conversion -6%. Now what?

Today's warm-up: Fraud Wall Calibration (Senior PM · Technical Acumen)

You tightened the fraud rules and chargebacks fell 40%. Victory — until new-user conversion fell 6% and the false positives turned out to concentrate in one acquisition channel. Risk says the losses were unsustainable and wants control by channel. Acquisition says that channel drives the volume; choking it isn't an option. Data science says a per-channel sub-model is feasible, but manual review adds delay. Channel-specific thresholds, a review queue, or roll the whole thing back? You fixed fraud and broke growth. Unbreak one without re-breaking the other.