FireDAC FDQuery Outer Join with fdUpdateSQL fails when Inserting Records

[BushAl 0]

I have a FDQuery with a left join between a cost Centre Table (CC) and an Estimate Detail Table (ED) that can have multiple records for a CC. The select is below for ref. The application should allow the ED to be updated and inserted (at simplest in a string grid). The Query will successfully update records in the ED, but fails when trying to insert, stating "update affected [0] rows, while [1] was requested". So I tried adding a FDUpdateSQL linked to the Query and an OnUpdateRecord as follows but it gives exactly the same error (also shown below)

if (ARequest = arUpdate) and (ASender.FieldByName('EstDtl_ID').IsNull) then
 begin
   ARequest := arInsert;
 end;

If anyone has any tips on how to force an insert under this condition I would be very grateful.

Project Builder.exe raised exception class EFDDBEngineException with message '[FireDAC][Phys][FB]-312. Exact update affected [0] rows, while [1] was requested'.

select b.*, a.csc_id as refcsc_id, a.cscdsc as cscdsc, a.cstpls as refcstpls, a.gstinc as refgstinc, a.gstpct as refgstpct from csc a left join estdtl b on a.csc_id = b.csc_id and b.est_id = !est_id