POST /rest/payment/{paymentId} - "Integrity constraint violation" occurs even if 'regenerateHash' is set to true

If a payment with exact details but different orderId is sent to /rest/payment/{paymentId}, even if setting `regenerateHash` to true I get:

`SQLSTATE[23000]: Integrity constraint violation: 1062 Duplicate entry '6527a....' for key 'hash'`