Posting a payment and applying multiple credits

I have a customer that has two invoices, both for $500.00.  I've applied a credit against both invoices for $1,000.00.  This shows up in QBO online properly, but now I want to apply a payment that uses that credit memo so it can apply it directly to the invoices.

My request looks like this:

{
"ARAccountRef": {
"name": "Accounts Receivable",
"value": "32"
},
"CustomerRef": {
"name": "Rob deMontarnal",
"value": "22"
},
"Line": [{
"Amount": 500,
"LinkedTxn": [{
"TxnId": 236,
"TxnType": "Invoice"
}, {
"TxnId": 239,
"TxnType": "CreditMemo"
}]
}, {
"Amount": 500,
"LinkedTxn": [{
"TxnId": 237,
"TxnType": "Invoice"
}, {
"TxnId": 239,
"TxnType": "CreditMemo"
}]
}],
"PaymentRefNum": "16,17",
"PrivateNote": "Linked payment to apply Credit #C945927470I\u000d\u000aCreditID: 239",
"TxnDate": "2022-09-25",
"domain": "QBO"
}

But I'm getting back this error:

{
"Fault": {
"Error": [{
"Message": "A business validation error has occurred while processing your request",
"Detail": "Business Validation Error: The Amount Received (plus credits) can't be less than the selected charges. Also, the selected charges can't be less than the selected credits.",
"code": "6000",
"element": ""
}],
"type": "ValidationFault"
},
"time": "2022-09-25T07:46:46.280-07:00"
}

I can't figure out what I'm doing wrong.  Any suggestions would be appreciated.