Access Run time error - '-2147352567 (80020009)': subform - vba

Question

I've created a form where I can use a subform to load data from a query into textboxes so I can edit the data one at a time and update the database. This usually works fine except I have a run time error that randomly appears now and then - '-2147352567 (80020009)': The value you entered isn't valid for this field.'
If I stop running it and try running it again it usually works fine until the same run-time error appears. It's very inconsistent.
Private Sub btn_SelectAgency_Click()
If Not (Me.qryAgencyWithoutMileagesub.Form.Recordset.EOF And Me.qryAgencyWithoutMileagesub.Form.Recordset.BOF) Then
'get data to textbox control
With Me.qryAgencyWithoutMileagesub.Form.Recordset
Me.txt_AgencyID = .Fields("Agency ID")
Me.txt_AgencyName = .Fields("Agency Name")
Me.txt_Address1 = .Fields("Address 1")
Me.txt_Address2 = .Fields("Address 2")
Me.txt_City = .Fields("City")
Me.txt_Postcode = .Fields("Postcode")
Me.txt_AgencyMileage = .Fields("Mileage")
Me.txt_AgencyID.Tag = .Fields("Agency ID")
End With
End If
Me.txt_AgencyMileage = ""
End Sub
Private Sub btn_Update_Click()
If Me.txt_AgencyMileage = "" Then
MsgBox "No mileage added, add now"
Cancel = True
Else
CurrentDb.Execute "UPDATE EstateAgent_tbl SET EstateAgent_AgentMileage = '" & Me.txt_AgencyMileage & "' where EstateAgent_AgentID=" & Me.txt_AgencyID.Tag
Me.txt_AgencyID = ""
Me.txt_AgencyName = ""
Me.txt_Address1 = ""
Me.txt_Address2 = ""
Me.txt_City = ""
Me.txt_Postcode = ""
Me.txt_AgencyMileage = ""
End If
qryAgencyWithoutMileagesub.Form.Requery
If Me.qryAgencyWithoutMileagesub.Form.Recordset.RecordCount = 0 Then
MsgBox "No agencies without mileage"
DoCmd.Close
End If
End Sub
The error is on this line
Me.txt_AgencyID = .Fields("Agency ID")
I would appreciate any help with this, thank you :)

Answer 1

Dim rs As DAO.Recordset
Set rs = Me.qryAgencyWithoutMileagesub.Form.RecordsetClone
'get data to textbox control
With rs
If .RecordCount > 0 Then
Me.txt_AgencyID = .Fields("Agency ID")
Me.txt_AgencyName = .Fields("Agency Name")
Me.txt_Address1 = .Fields("Address 1")
Me.txt_Address2 = .Fields("Address 2")
Me.txt_City = .Fields("City")
Me.txt_Postcode = .Fields("Postcode")
Me.txt_AgencyMileage = .Fields("Mileage")
Me.txt_AgencyID.Tag = .Fields("Agency ID")
End If
End With
Set rs = Nothing
DoCmd.RefreshRecord
DoCmd.RunCommand acCmdUndo
'You can it try. That worked for me!

Answer 2

Try to exclude Null values:
If Not IsNull(.Fields("Agency ID").Value) Then
Me.txt_AgencyID.Value = .Fields("Agency ID").Value
End If
You may also try using the RecordsetClone:
Dim rs As DAO.Recordset
Set rs = Me.qryAgencyWithoutMileagesub.Form.RecordsetClone
'get data to textbox control
With rs
If .RecordCount > 0 Then
Me.txt_AgencyID = .Fields("Agency ID")
Me.txt_AgencyName = .Fields("Agency Name")
Me.txt_Address1 = .Fields("Address 1")
Me.txt_Address2 = .Fields("Address 2")
Me.txt_City = .Fields("City")
Me.txt_Postcode = .Fields("Postcode")
Me.txt_AgencyMileage = .Fields("Mileage")
Me.txt_AgencyID.Tag = .Fields("Agency ID")
End If
End With
Set rs = Nothing