Thanks nostr:npub1xv8mzscll8vvy5rsdw7dcqtd2j268a6yupr6gzqh86f2ulhy9kkqmclk3x! I figured it was on Alby Hub's side of things, because the transactions I had attempted were going through once I restarted the Hub, so it was seeing the payment requests sitting on the relay as soon as it reconnected.