Seems like LN invoices included by Primal in zap receipts have empty payment_hash field. The invoice parser I use discards those invoices as invalid. I guess I'll have to patch it, as this is an optional field for zap verification purposes - they generate a proper invoice for the actual payment.

They also strip the description/commit hash from the invoice in zap receipts, which seems to go against nip57: "SHA256(description) MUST match the description hash in the bolt11 invoice." It looks like I will have to strip this verification logic on my end since in practice many wallets violate nip57 anyway and everyone is just trusting the wallets.