Why does a button control need to be clicked twice?

<asp:panel ID="Panel2" DefaultButton="btnPrvCmt" runat=server>
    <asp:Panel id="pnldetTI" runat="server" cssclass="collapsePanel" >
        <asp:UpdatePanel ID=upnlTransfers runat=server UpdateMode=Always>
            <ContentTemplate>
                <asp:GridView ID="gvFundIn" runat="server" AllowSorting="True" ShowFooter=true DataSourceID="sdsTransfers" DataKeyNames="FundsIn_ID,Last_Update_Date,Follow_Up_Date" AutoGenerateColumns="False" Width="510px" >
                    <Columns>

</Columns>
                    <EmptyDataTemplate>


                    </EmptyDataTemplate>
                </asp:GridView>
                    <asp:Panel ID="pnldvFundInActions" runat=server>
                        <br />
                        <div align=center>
                            <asp:Button ID="btnTIPending" runat="server" Width="215px" cssclass="input_btn_db" Text=" Transfer In Pending Items " OnCommand="btnPndItm_Click" CommandName="FundsIn" />
                            <br />
                        </div>
                        <br />
                        <div align=center>
                            <asp:Button ID="btnTIPrvCmt" runat="server" Width="215px" cssclass="input_btn_db" Text="Add Transfer In Comments " OnCommand="btnPrvCmt_Click" CommandName="FundsIn" />
                        </div>
                    </asp:Panel>
                </asp:Panel>
                <asp:SqlDataSource

                </asp:SqlDataSource>
            </ContentTemplate>
        </asp:UpdatePanel>
    </asp:Panel>
</asp:panel>

Protected Sub btnPndItm_Click(ByVal sender As Object, ByVal e As CommandEventArgs) Handles btnPndItm.Command
    If Not e.CommandName = "" Then
        sdsPndItm.SelectParameters("TYPE").DefaultValue = CType(e.CommandName, String)
    Else
        sdsPndItm.SelectParameters("TYPE").DefaultValue = "Account"
    End If
    If Not e.CommandArgument = "" Then
        sdsPndItm.SelectParameters("SecondID").DefaultValue = CType(e.CommandArgument, Integer)
    Else
        sdsPndItm.SelectParameters("SecondID").DefaultValue = CType(Session("AcctID"), Integer)
    End If
    sdsPndItm.DataBind()
    Panel2.Visible = False
    pnlPndItm.Visible = True
    'If Session("GroupID") = 4 Then
        gvPndItm.Columns(0).Visible = True
    'Else
    '    gvPndItm.Columns(0).Visible = False
    'End If
End Sub

Protected Sub btnPrvCmt_Click(ByVal sender As Object, ByVal e As CommandEventArgs) Handles btnPrvCmt.Command
    If Not e.CommandName = "" Then
        SqlDataSource5.SelectParameters("TYPE").DefaultValue = CType(e.CommandName, String)
        Session("PrvCmtType") = CType(e.CommandName, String)
    Else
        SqlDataSource5.SelectParameters("TYPE").DefaultValue = "Account"
        Session("PrvCmtType") = "Account"
    End If
    If Not e.CommandArgument = "" Then
        Session("SecondID") = CType(e.CommandArgument, Integer)
    Else
        Session("SecondID") = CType(Session("AcctID"), Integer)
    End If
    SqlDataSource5.DataBind()
    Panel2.Visible = False
    pnlPrvCmt.Visible = True
End Sub

protected override void OnInit(EventArgs e)
{
    var scriptManager = ScriptManager.GetCurrent(this);
    // or this.Page in a UserControl, etc.

    scriptManager.RegisterPostBackControl(someButton);
    scriptManager.RegisterPostBackControl(someOtherButton);
    // etc. for each control that needs to update something outside the UpdatePanel
}