Weird issue about self-defining function in VBA

PUBLIC dic As Object

Function P_query(spath, sFields, swhere, Optional wsName = "Sheet1")
'If Application.Calculation = xlCalculationAutomatic Then Application.Calculation = xlCalculationManual

  Dim rs As New ADODB.Recordset
  Dim sql$, itype$, val
  Dim arrResult
  Dim iscal As Boolean
  If iscal Then Exit Function Else iscal = True
  
  If dic Is Nothing Then Set dic = CreateObject("Scripting.Dictionary")
  P_query = Array("")
  If Len(sFields) = 0 Or sFields = "[]" Then Exit Function
  If Dir(spath, 16) = Empty Then MsgBox "数据源路径不存在": Exit Function
  If Len(swhere) > 0 Then swhere = " where " & swhere

  If Not dic.exists(spath) Then
    Dim cnn As ADODB.Connection
    Set cnn = New ADODB.Connection
    With cnn
      If Application.Version = "11.0" Then
        .Provider = "microsoft.jet.oledb.4.0"
        .ConnectionString = "extended properties=""excel 8.0;HDR=YES;IMEX=1"";data source=" & spath
      Else
        .Provider = "microsoft.ACE.oledb.12.0"
        .ConnectionString = "extended properties=""excel 12.0;HDR=YES;IMEX=1"";data source=" & spath
      End If
      .Open
    End With
    dic.Add spath, cnn
  End If
  
    sql = "select " & sFields & " from [" & wsName & "$]" & swhere
    rs.CursorLocation = adUseClient
    On Error GoTo err1
    rs.Open sql, dic(spath), 1, 1
    If rs.RecordCount = 0 Then P_query = "#N/A": rs.Close: Set rs = Nothing: Exit Function
    If rs.EOF Then rs.MoveFirst
    If rs.Fields(0).Type = 5 Then itype = "Double" Else itype = "String"
    val = rs.GetRows()
    P_query = IIf(IsNull(val(0, 0)), "#N/A", Format(val(0, 0), "standard"))
    rs.Close
    Set rs = Nothing
  Exit Function
err1:
    rs.Close
    Set rs = Nothing
    Set cnn = Nothing
    Set dic = Nothing
    Debug.Print "ERR" & "--" & Err.Description
    P_query = "#Value"
End Function