Problem with domain aggregate function in report giving blank results for proven query data

I have created a report that looks at patient charges/payments and gives the 'first' dates for billing, payments, and adjustments.  There is a master table fed by another application that gives a record per 'entry' - i.e. the initial charge for a procedure billed would be one line, the payment(s) would be other lines, and any adjustment(s) would be other lines.

I have 4 queries involved in this:
1) The main query that (modification of a duplicate query) that brakes down each patient per procedure billed
2) A breakdown of that query that gives the first procedure billed per patient
3) A query of the main table that groups the data by patient number, insurance plan, ref number, procedure code, ChargeType="PMT", and minimum post date, to get the first date payment posted
4) A query of the main table that groups the data by patient number, insurance plan, ref number, procedure code, ChargeType="ADJ", and minimum post date, to get the first date adjustment posted

I've been able to test the data in each query and confirm accuracy, but my problem is with a domain aggregate function used to pull the 1st payment and 1st adjustment dates from the last 2 queries.  Why are the records with no insurance plan code pulling neither of the dates that I can clearly see in the last 2 queries?... (see attached code for example of payment function, and all other records pull the appropriate data)Start Free Trial

1:

= IIf (IsEmpty ([FirstOfChg_Cv1_Plan_Code Field]),DMin("[AcctAct Payment Dates Query]![Date_Post]","[AcctAct Payment Dates Query]","[AcctAct Payment Dates Query]![Pat_Person_Nbr] = [FirstOfPat_Person_Nbr Field] AND  IsEmpty(Trim([AcctAct Payment Dates Query]![Chg_Cv1_Plan_Code])) AND  [AcctAct Payment Dates Query]![FirstOfDate_Svc_From] = [FirstOfFirstOfDate_Svc_From] AND [AcctAct Payment Dates Query]![Procedure_Code] =  [FirstOfFirstOfProcedure_Code]"),DMin("[AcctAct Payment Dates Query]![Date_Post]","[AcctAct Payment Dates Query]","[AcctAct Payment Dates Query]![Pat_Person_Nbr] = [FirstOfPat_Person_Nbr Field] AND  [AcctAct Payment Dates Query]![Chg_Cv1_Plan_Code] =  [FirstOfChg_Cv1_Plan_Code Field] AND  [AcctAct Payment Dates Query]![FirstOfDate_Svc_From] = [FirstOfFirstOfDate_Svc_From] AND [AcctAct Payment Dates Query]![Procedure_Code] =  [FirstOfFirstOfProcedure_Code]"))