Sporadic issue with ReportViewer - "A data source instance has not been supplied for the data source"

Hi. I have an application that has been working fine for at least 2 years. Around January of this year, some of our tech people made a bunch of changes in the virtual infrastructure, physical networking, etc. to the servers hosting our ASP.NET apps. After these changes (of which there were far too many to be able to isolate), I am now having problems with one of my apps

The app uses a ReportViewer control to display a report. It works most of the time, but sporadically, and such that I can't reproduce it, the users will get an error "A data source instance has not been supplied for the data source", and the report will not display. I am trying to figure out how to either 1) find out from Windows error logs or some other method what is causing this to happen, or 2) be able to work around it so that the user can try to re-run the report if it happens. Here is a sample of the code I am using. I have added the Try...Catch block and the display of a "try again" button to let them try the report again. This error-handling change has not been pushed out yet, so I am not sure if this will help, but I hope so, at least so they can try again. The report they complain about not working the most is the one handled by the report type "KeyReturn" in the code.

Please advise if there is a particular Windows error log I can try to look at to see what is causing this problem, or if there is some other way that I don't know about that I can use to prevent this from happening. Thank you.

    Protected Sub PrintReport()
        Dim BadCall As Boolean = False

        Try
            rvReportViewer.LocalReport.DataSources.Clear()
            Select Case lblRepType.Text
                Case "KeyReceipt"
                    rvReportViewer.LocalReport.ReportPath = "Reports\KeyReceipt.rdlc"

                    Dim reportParameters(0) As ReportParameter
                    reportParameters(0) = New ReportParameter("Building", lblBuildingName.Text)
                    rvReportViewer.LocalReport.SetParameters(reportParameters)

                    ObjectDSKeyReceipt.SelectParameters("CustID").DefaultValue = lblCustID.Text
                    ObjectDSKeyReceipt.SelectParameters("Building").DefaultValue = lblBuildingCode.Text
                    ObjectDSKeyReceipt.SelectParameters("incident").DefaultValue = lblRepOptions.Text
                    ObjectDSKeyReceipt.SelectParameters("RepDate").DefaultValue = lblRepOptions2.Text
                    ''
                    ObjectDSKeyReceiptSubKeycode.SelectParameters("CustID").DefaultValue = lblCustID.Text
                    ObjectDSKeyReceiptSubKeycode.SelectParameters("Building").DefaultValue = lblBuildingCode.Text
                    ObjectDSKeyReceiptSubKeycode.SelectParameters("incident").DefaultValue = lblRepOptions.Text
                    ObjectDSKeyReceiptSubKeycode.SelectParameters("RepDate").DefaultValue = lblRepOptions2.Text
                    ''
                    ObjectDSKeyReceiptSubCurrentCharge.SelectParameters("CustID").DefaultValue = lblCustID.Text
                    ObjectDSKeyReceiptSubCurrentCharge.SelectParameters("Building").DefaultValue = lblBuildingCode.Text
                    ObjectDSKeyReceiptSubCurrentCharge.SelectParameters("incident").DefaultValue = lblRepOptions.Text
                    ObjectDSKeyReceiptSubCurrentCharge.SelectParameters("RepDate").DefaultValue = lblRepOptions2.Text

                    rvReportViewer.LocalReport.DataSources.Add(New ReportDataSource("DataSetKeyReceipt", "ObjectDSKeyReceipt"))
                    AddHandler rvReportViewer.LocalReport.SubreportProcessing, AddressOf SetKeyReceiptSubDataSource
                Case "KeyReturn"
                    rvReportViewer.LocalReport.ReportPath = "Reports\KeyReturn.rdlc"

                    Dim reportParameters(0) As ReportParameter
                    reportParameters(0) = New ReportParameter("Building", lblBuildingName.Text & " Key Receipt")
                    rvReportViewer.LocalReport.SetParameters(reportParameters)

                    ObjectDSKeyReturn.SelectParameters("CustID").DefaultValue = lblCustID.Text
                    ObjectDSKeyReturn.SelectParameters("Building").DefaultValue = lblBuildingCode.Text
                    ObjectDSKeyReturn.SelectParameters("incident").DefaultValue = lblRepOptions.Text
                    ObjectDSKeyReturn.SelectParameters("RepDate").DefaultValue = lblRepOptions2.Text
                    ''
                    ObjectDSKeyReturnSubCharges.SelectParameters("CustID").DefaultValue = lblCustID.Text
                    ObjectDSKeyReturnSubCharges.SelectParameters("Building").DefaultValue = lblBuildingCode.Text
                    ObjectDSKeyReturnSubCharges.SelectParameters("incident").DefaultValue = lblRepOptions.Text
                    ObjectDSKeyReturnSubCharges.SelectParameters("RepDate").DefaultValue = lblRepOptions2.Text

                    rvReportViewer.LocalReport.DataSources.Add(New ReportDataSource("DataSetKeyReturn", "ObjectDSKeyReturn"))
                    AddHandler rvReportViewer.LocalReport.SubreportProcessing, AddressOf SetKeyReturnSubDataSource
                Case "LateKeyNotification"
                    rvReportViewer.LocalReport.ReportPath = "Reports\LateKey.rdlc"

                    Dim reportParameters(0) As ReportParameter
                    reportParameters(0) = New ReportParameter("Building", lblBuildingName.Text)
                    rvReportViewer.LocalReport.SetParameters(reportParameters)

                    ObjectDSLateKey.SelectParameters("CustID").DefaultValue = lblCustID.Text
                    ObjectDSLateKey.SelectParameters("Building").DefaultValue = lblBuildingCode.Text
                    ObjectDSLateKey.SelectParameters("incident").DefaultValue = lblRepOptions.Text

                    rvReportViewer.LocalReport.DataSources.Add(New ReportDataSource("DataSetLateKey", "ObjectDSLateKey"))
                Case "KeysOut"
                    rvReportViewer.LocalReport.ReportPath = "Reports\KeysOut.rdlc"

                    Dim reportParameters(0) As ReportParameter
                    reportParameters(0) = New ReportParameter("BuildingName", lblBuildingName.Text)
                    rvReportViewer.LocalReport.SetParameters(reportParameters)

                    ObjectDSKeysOut.SelectParameters("Building").DefaultValue = lblBuildingCode.Text

                    rvReportViewer.LocalReport.DataSources.Add(New ReportDataSource("DataSetKeysOut", "ObjectDSKeysOut"))
                Case Else
                    BadCall = True
            End Select
            If Not BadCall Then
                rvReportViewer.ProcessingMode = ProcessingMode.Local
                rvReportViewer.Visible = True
                rvReportViewer.LocalReport.Refresh()
            Else
                divReports.Visible = False
                divButtons.Visible = True
                lblError.Text = "There was an error calling this page to print a report. Please close the window/tab. Report requested was " & lblRepType.Text
                btnReprintReport.Visible = False
            End If
        Catch ex As Exception
            divReports.Visible = False
            divButtons.Visible = True
            lblError.Text = "There was an error calling this page to print a report. Please close the window/tab, or try the report again. " &"Report requested was '" & lblRepType.Text & "'. The error reported was: " & ex.Message
            btnReprintReport.Visible = True
        End Try
    End Sub

    Protected Sub SetKeyReceiptSubDataSource(ByVal sender As Object, ByVal e As SubreportProcessingEventArgs)
        e.DataSources.Add(New ReportDataSource("DataSetKeyReceipt_SubReportKeycode", "ObjectDSKeyReceiptSubKeycode"))
        e.DataSources.Add(New ReportDataSource("DataSetKeyReceipt_SubReportCurrentCharge", "ObjectDSKeyReceiptSubCurrentCharge"))
        e.DataSources.Add(New ReportDataSource("DataSetKeyReceipt_SubReportRecoreCharges", "ObjectDSKeyReceiptSubRecoreCharges"))
    End Sub

    Protected Sub SetKeyReturnSubDataSource(ByVal sender As Object, ByVal e As SubreportProcessingEventArgs)
        e.DataSources.Add(New ReportDataSource("DataSetKeyReturn_SubReportCharges", "ObjectDSKeyReturnSubCharges"))
    End Sub