"Another process has updated the 'SOOrder' record. Your changes will be lost."

Since you’re inheriting the RunCaptureActions method from ARPaymentAfterProcessingManager, you don’t need to use PXOverride. That can only be used in a graph extension.

In this statement, you’re using aRPaymentEntry as the graph to select cCProcTran, but attempting to update it in soEntry. I’d recommend selecting from soEntry.

CCProcTran cCProcTran = SelectFrom<CCProcTran>.
    Where<CCProcTran.refNbr.IsEqual<@P.AsString>.
        And<CCProcTran.pCTranNumber.IsEqual<@P.AsString>>>.
    View.ReadOnly.Select(aRPaymentEntry, aRPayment.RefNbr, "key");
 if (cCProcTran != null)
 {
     cCProcTran.Amount = totalamt;
     soEntry.ccProcTran.Update(cCProcTran);
 }

Same with this one:

ExternalTransaction externalTransaction = SelectFrom<ExternalTransaction>.
    Where<ExternalTransaction.refNbr.IsEqual<@P.AsString>.
        And<ExternalTransaction.tranNumber.IsEqual<@P.AsString>>>.
    View.ReadOnly.Select(aRPaymentEntry, aRPayment.RefNbr, "key");
 if (externalTransaction != null)
 {
     externalTransaction.Amount = totalamt;
     externalTransaction.SyncMessage = string.Empty;
     soEntry.ExternalTran.Update(externalTransaction);
 }

Not certain this is causing the error, but I’d fix those to start with.

Also, aRPayment and sOAdjust aren’t initialized in the code you posted, but I’d make sure you aren’t cross contaminating caches with those as well.

​@darylbowman 

I made the following changes and no longer get the "Another process has updated the 'SOOrder' record. Your changes will be lost." error.
Because the graph in the current thread is an ARPaymentEntry, I had to use the following method to retrieve the cached data: graph.Caches<SOOrder>().Cached.Cast<SOOrder>().FirstOrDefault()
When saving, use:
soEntry.TimeStamp = soOrder.tstamp;
Is this the best approach?

Also, when calling soEntry.Adjustments.Update(sOAdjust);, I get the "AR Error: Entry must be less than or equal to 500.0000" error.
It seems this validation is done in Acumatica's SOAdjust_CuryAdjdAmt_FieldVerifying.
How can I circumvent it?

public override void RunCaptureActions(IBqlTable table, bool success)
   {
       ARPaymentEntry graph = base.CreateGraphIfNeeded(table);
       FunctionA(graph, table);
       base.RunCaptureActions(table, success);
   }

private void FunctionA(ARPaymentEntry graph, IBqlTable table)
{
    PX.Objects.AR.ARPayment aRPayment = table as PX.Objects.AR.ARPayment;
    SOOrderEntry soEntry = PXGraph.CreateInstance<SOOrderEntry>();
    SOOrder soOrder=graph.Caches<SOOrder>().Cached.Cast<SOOrder>().FirstOrDefault();
    SOAdjust sOAdjust = graph.Caches<SOAdjust>().Cached.Cast<SOAdjust>().FirstOrDefault();
    soEntry.Document.Current = soOrder;
    soEntry.Adjustments.Current = sOAdjust;

    CCProcTran cCProcTran = SelectFrom<CCProcTran>.Where<CCProcTran.refNbr.IsEqual<@P.AsString>>.View.ReadOnly.Select(soEntry, aRPayment.RefNbr);

    decimal testamount = 5m;
    SOLine soLine = new SOLine();
    soLine.InventoryID = 10322;
    soLine.OrderNbr = soOrder.OrderNbr;
    soLine.OrderType = soOrder.OrderType;
    soLine.BranchID = soOrder.BranchID;
    soLine.Qty = 1;
    soLine.CuryUnitPrice = testamount;
    soLine.CuryExtPrice = testamount;
    soLine = soEntry.Transactions.Insert(soLine);

    PFESOLine_Ext solineExt = soLine.GetExtension<PFESOLine_Ext>();
    solineExt.UsrPFETempPaymentKey = $"{aRPayment.DocType}-{aRPayment.RefNbr}";
    soLine = soEntry.Transactions.Update(soLine);
    decimal FinalAmount = 505m;
    if (cCProcTran != null)
    {
        cCProcTran.Amount = FinalAmount;
        soEntry.ccProcTran.Update(cCProcTran);
    }
    ExternalTransaction externalTransaction = SelectFrom<ExternalTransaction>.Where<ExternalTransaction.refNbr.IsEqual<@P.AsString>>.View.ReadOnly.Select(soEntry, aRPayment.RefNbr);
    if (externalTransaction != null)
    {
        externalTransaction.Amount = FinalAmount;
        externalTransaction.SyncMessage = string.Empty;
        soEntry.ExternalTran.Update(externalTransaction);
    }
    sOAdjust.CuryAdjdAmt = FinalAmount;
    sOAdjust.CuryOrigDocAmt = FinalAmount;
    soEntry.Adjustments.Update(sOAdjust);
    soLine = soEntry.Transactions.Insert(soLine);
    if (soEntry.TimeStamp != soOrder.tstamp)
    {
        soEntry.TimeStamp = soOrder.tstamp;
    }
    if (soEntry.Adjustments.Current.tstamp != sOAdjust.tstamp)
    {
        soEntry.Adjustments.Current.tstamp = sOAdjust.tstamp;
    }
    soEntry.Save.Press();

    graph.Document.Current = aRPayment;
    aRPayment.CuryOrigDocAmt = FinalAmount;
    graph.Document.Cache.Update(aRPayment);

    graph.Save.Press();
}

​@AndrewZ 

You are updating your amount for the Sales Order which must be lowering the total to below what is already applied, or the amount on the payment is 500 and your new Sales Order value is above it.

You should update your aRPayment.CuryOrigDocAmt first, then update sOAdjust.CuryAdjdAmt.

You will also need to find the ARAdjust record, and update the CuryAdjgAmt field, otherwise, your document will be out of balance.

There is no associated ARAdjust in the ARPayment in SOOrder. In addition, there is a validation event SOAdjust_CuryAdjdAmt_FieldVerifying in the Acumatica source code for CuryAdjdAmt. This event verifies itself and the modified value. I updated the balance in an attempt to circumvent it.

I not certain of the situation, but you could write a blank FieldVerifying extension handler and simply not call the base, or more complex logic, depending upon your needs.