How this loses money

The rate is set by whichever side of the market is crowded. When shorts are crowded, shorts pay. A vault built to receive funding will, in those stretches, be paying it — and the position has no price gain to offset that, because the position has no price exposure by design.

The short is a margined position. A fast enough rally can push it past its maintenance margin and close it out. The moment that happens the hedge is gone and the vault is holding the coin outright — long, in a market that just spiked, which is the worst moment to be unhedged.

The short leg lives somewhere. Whoever holds it can halt withdrawals, be hacked, be seized, or become insolvent while your position is open. Holding the coin on the other side does not protect you from losing the leg that was hedging it.

Entering and exiting means two trades in two markets. Between them the price moves, spreads widen, and size gets filled worse than quoted. That gap is a real cost and it is largest exactly when markets are disorderly.

Every rebalance pays fees and crosses a spread. In a low-funding regime the yield can be smaller than the cost of staying neutral, and the position grinds down slowly while doing precisely what it was designed to do.

The hedge assumes the two prices track each other. Under stress they can decouple for long enough to matter, and a position that is neutral on paper stops being neutral in practice.

Vault logic can be wrong. Access controls can be wrong. An upgrade key, if one exists, is a person or a multisig who can change what the contract does after you deposit. An audit reduces this risk; it does not remove it.

A withdrawal has to unwind both legs. If the market is thin, or the venue is degraded, or the position is large relative to available liquidity, that takes time or costs a lot — and the moment you most want to leave is the moment both are worst.