VC Expression based on Child Table returns 0 when value is present

[Daisy_Ramirez]

I have a simple virtual column in my Quotes Header table (data type: price) that should display the SUM value of a field (data type: price) in a related table Commissions. According to the client the issue is sporadic. Here’s the formula:

SUM(SELECT(Commissions[Com Pay],AND([Sales Rep]=[_THISROW].[Assigned to],[Quote]=[_THISROW].[quote_id])))

-The expression returns no errors
-Confirmed there is a value in the Com Pay field
-Confirmed Quote Assigned to = Commission Sales Rep
-Confirmed Quote quote_id = Commissions Quote

Is there another dependable way of writing this expression?

Thank you