Unable to add records more than 28 in access database - vb.net

Question

I am making my first project using vb.net and access. I am trying to develop a project in which the data of patients of the is added from different counters.it works fine till 22nd or 23rd record entered. after that adding new record over writes the last saved record.
to check the database i deleted some record (say after deletion there are 13 records left in the database) and tried to add new record, it gives the same problem, the 13th record is overwritten by the new record.
i deleted all the records and tried to add new record, the first record successfully entered but after that new record entry over writes the last (only) record.
i'm unable to understand the problem
code for saving data is
Private Sub Save()
'Dim st As String
Dim str As String
btnSave_Click = False
str = check
If Not str = "" Then
MsgBox(str, vbInformation, "Patient Registration")
btnSave_Click = False
Exit Sub
End If
If conn.State = 0 Then
Module1.openConnection()
End If
If Not rsDept Is Nothing Then
If rsDept.State = 0 Then
Call openRecordset("SELECT * FROM tblDept", rsDept)
End If
Else
Call openRecordset("SELECT * FROM tblDept", rsDept)
End If
If Not rsData Is Nothing Then
If rsData.State = 0 Then
Call openRecordset("Select * from tblPatientRecord", rsData)
End If
Else
Call openRecordset("Select * from tblPatientRecord", rsData)
End If
conn.BeginTrans()
On Error GoTo ProcError
If Not (rsData.BOF And rsData.EOF) Then
rsData.MoveLast()
Call addData(rsData)
Else
Call addData(rsData)
End If
conn.CommitTrans()
MsgBox("Patient's Record Saved Successfully...!", MsgBoxStyle.Information, "Patient Registration")
Call loadDataListview()
Call fieldDisable()
Call Disable_SearchButtons()
btnSave_Click = True
comDepart.Enabled = False
conn.Close()
ProcError:
If Err.Number <> 0 Then
conn.RollbackTrans()
MsgBox(Err.Number & " " & Err.Description)
Call addNewR()
Exit Sub
End If
End Sub
Private Sub addData(rData As ADODB.Recordset)
Dim rsPaymentType As New ADODB.Recordset
'Dim str As String
If Not (rData.BOF And rsData.EOF) Then
rData.MoveFirst()
If rData.RecordCount > 0 Then
Do
If txthn.Text = rData("hNumber").Value Then
Call addVisit()
conn.Execute("update tblPatientRecord set visitNo = '" & vNo.Text & "' where hNumber = '" & txthn.Text & "'")
Call fieldEnable()
Exit Sub
End If
rData.MoveNext()
Loop Until rData.EOF
End If
End If
rData.AddNew()
rData("hNumber").Value = txthn.Text
rData("fName").Value = txtfn.Text
rData("contactNo").Value = txtContact.Text
rData("address").Value = txtaddress.Text
rData("cnic").Value = txtcnic.Text
'rData("cnic").Value = rCNIC()
rsData("visitNo").Value = vNo.Text
rsData("cnicSD").Value = comSD.Text
''Add gender as selected
If radmale.Checked = True Then
rData("gender").Value = radmale.Text
ElseIf radfemale.Checked = True Then
rData("gender").Value = radfemale.Text
Else
rData("gender").Value = " - "
End If
If txtAge.Text < 105 Or Year(dtAgePicker.Value) < 1915 Then
Call addAge()
'MsgBox("data of tblAge added")
Else
MsgBox("Please Enter Correct Age ", vbCritical, "")
txtAge.Select()
Exit Sub
End If
If comRelation.Text = "Select Relation with Patient" Or comRelation.Text = "" Then
comRelation.Text = "Not Selected"
End If
If txtfh.Text = "" Then
txtfh.Text = "Not Given"
End If
Call addRelation()
'Save Department ID as selected
If comDepart.Text <> "Select Department" Then
Call addVisit()
'MsgBox("data of tblVisit added")
Else
MsgBox("Please Enter the Department ", vbCritical, "")
comDepart.Select()
Exit Sub
End If
If Not rsPaymentType Is Nothing Then
If rsPaymentType.State = 0 Then
Call openRecordset("Select * from tblPaymentType", rsPaymentType)
'MsgBox("Patient record is open" & rsData.State)
End If
Else
Call openRecordset("Select * from tblPaymentType", rsPaymentType)
'MsgBox("Patient record is open")
End If
If Not (rsPaymentType.BOF And rsPaymentType.EOF) Then
rsPaymentType.MoveFirst()
Do
If rsPaymentType("paymentType").Value = comPaymentType.Text Then
rData("paymentType").Value = rsPaymentType("paymentTypeID").Value
Exit Do
Else
rData("paymentType").Value = 0
End If
rsPaymentType.MoveNext()
Loop Until rsPaymentType.EOF
End If
rsData.Update()
End Sub
Public Function h_N0_Generator(rs As ADODB.Recordset) As String
Dim str, p1() As String
Dim auto_long As Long
Dim hMonth As String
Dim strCounter As String, temp As String
'this counter file is added to make the hNumber unique for multiple counter /* in the file counter number is added and have respective counter number only*/
FileOpen(FileNum, "C048ounter.txt", OpenMode.Input)
strCounter = LineInput(FileNum)
FileClose(FileNum)
If strCounter = "" Then
strCounter = "1"
End If
hMonth = Month(Now).ToString("D2")
If (rs.EOF And rs.BOF) Then
h_N0_Generator = "NIRM-" & Year(Now) & "-" & hMonth & "-" & "00000" & strCounter
Else
rs.MoveLast()
str = rs("HNumber").Value
p1 = str.Split("-")
' check if the current month is the same as in last stored Hospital No or not
'if yes the last five digits increment otherwise it restarts with 0
If p1(2) = Month(Now) And p1(1) = Year(Now) Then
temp = Right(rs(0).Value, 6)
auto_long = Left(temp, 5) + 1
h_N0_Generator = "NIRM-" & Year(Now) & "-" & hMonth & "-" & Right("00000" & auto_long, 5) & strCounter
Else
h_N0_Generator = "NIRM-" & Year(Now) & "-" & hMonth & "-" & "00000" & strCounter
End If
End If
'Return auto_num
End Function