USM's defund() redemption function contains a pricing flaw that makes payout size depend on how a FUM redemption is split, creating a path for 64 small withdrawals to extract far more ETH than one large withdrawal. The issue lies in ethFromDefund(), which values a single redemption using the arithmetic average of the current FUM sell price and the estimated terminal FUM sell price. SlowMist Team said that approach lacks split invariance (same total result regardless of how an amount is divided), and the distortion grows further when the single-redemption state shrink coefficient adjShrinkFactor and integer rounding are applied.