Where the losses actually came from
Exchange failures, custodial insolvency, stablecoin de-pegs, bridge exploits, and frozen withdrawals. A market-neutral book with perfect execution is fully exposed to every one of these, because the exposure is to the venue rather than to the price.
Why this resists automation
Counterparty risk is assessed on disclosure quality, jurisdiction, audit history, and reputation. None of that is a data feed. A machine can monitor withdrawal latency and proof-of-reserve attestations as leading indicators, but the decision to reduce exposure to a venue is a judgement call.
The structural mitigation
Limit per-venue exposure to a figure whose total loss would be survivable, and treat that limit as a hard constraint the strategy cannot argue with. This caps returns. It is the trade every operator who is still trading has made.