Why might my ADODB.Recordset suddenly quit adding new records?

[firebirdxvi]

My ADODB.Recordset is being populated as desired for 5 records, then all subsequent records don't get added anywhere. I checked in debug and the code runs through this loop the desired 8 times, but only adds a record the first 5.

Any ideas why this is happening to me?

With doc.Tables(8)
For I = 2 to .Rows.Count
S.AddNew

S![PN] = .Cell(I,3).Range.Text
'and more lines like this ^

S.Update
Next
End With

Thanks for any input!

[firebirdxvi]

SOLVED.

I had accidentally set a field as Indexed (No Duplicates) which kept the last few records from adding.

Thanks for reading my question.