Vb - HttpRequest Maximum Length Exceeded In ASP

I'm trying to fix an issue with an application I'm supporting (I didn't write the code). The code takes an SSRS report and renders it in pdf format. Users are sporadically getting the error indicated in the title. There is no rhyme or reason to when the error is generated (a particular report will run one time and throw the error the next). The code is below.

Public Sub OpenReport()
Dim MyParms As New Generic.List(Of ReportParameter)
Dim mimeType As String = Nothing
Dim encoding As String = Nothing
Dim extension As String = Nothing
Dim deviceInfo As String = Nothing
Dim streamids() As String = Nothing
Dim warnings As Microsoft.Reporting.WebForms.Warning() = Nothing
Dim bytes() As Byte
Dim format As String = "PDF" ''#to open the report in pdf; report viewer invisible
Try
If dropReports.SelectedItem.Value = "1" Then
If Session("IsBDAP") = True Then
MyParms.Add(New ReportParameter("SCAId", dropSCA.SelectedItem.Value, False))
Else
MyParms.Add(New ReportParameter("SCAId", Server.UrlEncode(Session("SCAId")), False))
End If
MyParms.Add(New ReportParameter("ProviderId", dropProvider.SelectedItem.Value, False))
If dropVisit.Visible = True Then
MyParms.Add(New ReportParameter("VisitId", dropVisit.SelectedItem.Value, False))
End If
MyParms.Add(New ReportParameter("FY", dropContractFY.SelectedItem.Value, False))
ReportViewer1.ProcessingMode = ProcessingMode.Remote
ReportViewer1.ServerReport.ReportServerUrl = New Uri(System.Configuration.ConfigurationManager.AppSettings("ReportServerURI"))
ReportViewer1.ServerReport.ReportPath = Session("ReportsFolder") & "MReport"
ReportViewer1.ServerReport.ReportServerCredentials = New MyReportServerCredentials()
ReportViewer1.ServerReport.SetParameters(MyParms)
''#Code to convert the report to pdf
deviceInfo = "<DeviceInfo>" + "<SimplePageHeaders>True</SimplePageHeaders>" + "</DeviceInfo>"
bytes = ReportViewer1.ServerReport.Render(format, deviceInfo, mimeType, encoding, extension, streamids, warnings)
Dim size As Integer = bytes.Length
ReportViewer1.ServerReport.Refresh()
Response.Buffer = True
Response.Clear()
Response.ContentType = mimeType
Response.AddHeader("content-disposition", "attachment; filename=MReport." + extension)
Response.BinaryWrite(bytes)
ElseIf dropReports.SelectedItem.Value = "2" Then
If Session("IsBDAP") = True Then
MyParms.Add(New ReportParameter("SCAId", dropSCA.SelectedItem.Value, False))
Else
MyParms.Add(New ReportParameter("SCAId", Server.UrlEncode(Session("SCAId")), False))
End If
MyParms.Add(New ReportParameter("ProviderId", dropProvider.SelectedItem.Value, False))
If dropVisit.Visible = True Then
MyParms.Add(New ReportParameter("FollowUpVisitId", dropVisit.SelectedItem.Value, False))
End If
MyParms.Add(New ReportParameter("FY", dropContractFY.SelectedItem.Value, False))
ReportViewer1.ProcessingMode = ProcessingMode.Remote
ReportViewer1.ServerReport.ReportServerUrl = New Uri(System.Configuration.ConfigurationManager.AppSettings("ReportServerURI"))
ReportViewer1.ServerReport.ReportPath = Session("ReportsFolder") & "FReport"
ReportViewer1.ServerReport.ReportServerCredentials = New MyReportServerCredentials()
ReportViewer1.ServerReport.SetParameters(MyParms)
''#Code to convert the report to pdf
deviceInfo = "<DeviceInfo>" + "<SimplePageHeaders>True</SimplePageHeaders>" + "</DeviceInfo>"
bytes = ReportViewer1.ServerReport.Render(format, deviceInfo, mimeType, encoding, extension, streamids, warnings)
ReportViewer1.ServerReport.Refresh()
Response.Buffer = True
Response.Clear()
Response.ContentType = mimeType
Response.AddHeader("content-disposition", "attachment; filename=FReport." + extension)
Response.BinaryWrite(bytes)

I read that the default length limit is 4MB. None of the reports by themselves are even over 350K. I'm wondering if this could be caused by a caching issue. I'm not an expert, so I need some guidance as to how best to solve the problem. I also want to understand why the issue is happening. note that only 2 reports are shown in the snippet - there are about 30+ reports in the full sub. edit - I tried the proposed solution, but it didn't help (I also tried the Fiddler route, but did not see anything glaring). I thought it might be best to clarify. The reports will run fine for a while, but the execution time gradually gets slower and slower until the application eventually displays the error.