I don't use macros,but it sounds like something needs to be refreshed when the button on parent to go to next record is clicked.
Your description is suggesting that it is processing all records in the related subform before the button click action is executed???
Can you post a copy of your database and describe how to get to a specific record to see the "issue"?
Good luck.
UPDATE:
I mocked up a situation with Mainform (Authors) and SubForm (AuthorBooks) with a button on the mainform to
Go To Next MainForm record. This is done with vba, but works as expected. It does not iterate/process each subform
record before going to next mainform record.
vba code associated with the button click event
Code:
' ----------------------------------------------------------------
' Procedure Name: btnGetNext_Click
' Purpose: Demo of buttom on main form that when clicked
' goes to next main form record. If at the end
' of the main form recordsource, present a message
' saying "no more records"
' Procedure Kind: Sub
' Procedure Access: Private
' Author: Jack
' Date: 27-Nov-19
' ----------------------------------------------------------------
Private Sub btnGetNext_Click()
10 On Error GoTo btnGetNext_Click_Error
20 DoCmd.GoToRecord , , acNext
30 On Error GoTo 0
40 Exit Sub
btnGetNext_Click_Error:
50 If Err.Number = 2105 Then
60 MsgBox "There are no more Author records", vbOKOnly
70 Else
80 MsgBox "Error " & Err.Number & " (" & Err.Description _
& ") in procedure btnGetNext_Click, line " & Erl & "."
90 End If
End Sub
Here's a screen capture showing message when attempting to go beyond the last Author record.