I'm facing the same issue. Seems if users have old purchase records and have made new purchase recently, their original_transaction_id returned by the API is different from the one at the time of purchase. Because this problem has a significant impact to our subscription management system, I hope you provide some guidance as soon as possible. Regards,

Apple reported me that there were some data issues causing incorrect OriginalTransactionID returned, and they've already fixed the root cause of that issue. So, I think what we should do is correct the OriginalTransactionID that were incorrectly stored in our DB.